// Package revision extracts git revision from string
// More information about revision : https://www.kernel.org/pub/software/scm/git/docs/gitrevisions.html
package revision

import (
        "bytes"
        "fmt"
        "io"
        "regexp"
        "strconv"
        "time"
)

// ErrInvalidRevision is emitted if string doesn't match valid revision
type ErrInvalidRevision struct {
        s string
}

func (e *ErrInvalidRevision) Error() string {
        return "Revision invalid : " + e.s
}

// Revisioner represents a revision component.
// A revision is made of multiple revision components
// obtained after parsing a revision string,
// for instance revision "master~" will be converted in
// two revision components Ref and TildePath
type Revisioner interface {
}

// Ref represents a reference name : HEAD, master, <hash>
type Ref string

// TildePath represents ~, ~{n}
type TildePath struct {
        Depth int
}

// CaretPath represents ^, ^{n}
type CaretPath struct {
        Depth int
}

// CaretReg represents ^{/foo bar}
type CaretReg struct {
        Regexp *regexp.Regexp
        Negate bool
}

// CaretType represents ^{commit}
type CaretType struct {
        ObjectType string
}

// AtReflog represents @{n}
type AtReflog struct {
        Depth int
}

// AtCheckout represents @{-n}
type AtCheckout struct {
        Depth int
}

// AtUpstream represents @{upstream}, @{u}
type AtUpstream struct {
        BranchName string
}

// AtPush represents @{push}
type AtPush struct {
        BranchName string
}

// AtDate represents @{"2006-01-02T15:04:05Z"}
type AtDate struct {
        Date time.Time
}

// ColonReg represents :/foo bar
type ColonReg struct {
        Regexp *regexp.Regexp
        Negate bool
}

// ColonPath represents :./<path> :<path>
type ColonPath struct {
        Path string
}

// ColonStagePath represents :<n>:/<path>
type ColonStagePath struct {
        Path  string
        Stage int
}

// Parser represents a parser
// use to tokenize and transform to revisioner chunks
// a given string
type Parser struct {
        s                 *scanner
        currentParsedChar struct {
                tok token
                lit string
        }
        unreadLastChar bool
}

// NewParserFromString returns a new instance of parser from a string.
func NewParserFromString(s string) *Parser {
        return NewParser(bytes.NewBufferString(s))
}

// NewParser returns a new instance of parser.
func NewParser(r io.Reader) *Parser {
        return &Parser{s: newScanner(r)}
}

// scan returns the next token from the underlying scanner
// or the last scanned token if an unscan was requested
func (p *Parser) scan() (token, string, error) {
        if p.unreadLastChar {
                p.unreadLastChar = false
                return p.currentParsedChar.tok, p.currentParsedChar.lit, nil
        }

        tok, lit, err := p.s.scan()

        p.currentParsedChar.tok, p.currentParsedChar.lit = tok, lit

        return tok, lit, err
}

// unscan pushes the previously read token back onto the buffer.
func (p *Parser) unscan() { p.unreadLastChar = true }

// Parse explode a revision string into revisioner chunks
func (p *Parser) Parse() ([]Revisioner, error) {
        var rev Revisioner
        var revs []Revisioner
        var tok token
        var err error

        for {
                tok, _, err = p.scan()

                if err != nil {
                        return nil, err
                }

                switch tok {
                case at:
                        rev, err = p.parseAt()
                case tilde:
                        rev, err = p.parseTilde()
                case caret:
                        rev, err = p.parseCaret()
                case colon:
                        rev, err = p.parseColon()
                case eof:
                        err = p.validateFullRevision(&revs)

                        if err != nil {
                                return []Revisioner{}, err
                        }

                        return revs, nil
                default:
                        p.unscan()
                        rev, err = p.parseRef()
                }

                if err != nil {
                        return []Revisioner{}, err
                }

                revs = append(revs, rev)
        }
}

// validateFullRevision ensures all revisioner chunks make a valid revision
func (p *Parser) validateFullRevision(chunks *[]Revisioner) error {
        var hasReference bool

        for i, chunk := range *chunks {
                switch chunk.(type) {
                case Ref:
                        if i == 0 {
                                hasReference = true
                        } else {
                                return &ErrInvalidRevision{`reference must be defined once at the beginning`}
                        }
                case AtDate:
                        if len(*chunks) == 1 || hasReference && len(*chunks) == 2 {
                                return nil
                        }

                        return &ErrInvalidRevision{`"@" statement is not valid, could be : <refname>@{<ISO-8601 date>}, @{<ISO-8601 date>}`}
                case AtReflog:
                        if len(*chunks) == 1 || hasReference && len(*chunks) == 2 {
                                return nil
                        }

                        return &ErrInvalidRevision{`"@" statement is not valid, could be : <refname>@{<n>}, @{<n>}`}
                case AtCheckout:
                        if len(*chunks) == 1 {
                                return nil
                        }

                        return &ErrInvalidRevision{`"@" statement is not valid, could be : @{-<n>}`}
                case AtUpstream:
                        if len(*chunks) == 1 || hasReference && len(*chunks) == 2 {
                                return nil
                        }

                        return &ErrInvalidRevision{`"@" statement is not valid, could be : <refname>@{upstream}, @{upstream}, <refname>@{u}, @{u}`}
                case AtPush:
                        if len(*chunks) == 1 || hasReference && len(*chunks) == 2 {
                                return nil
                        }

                        return &ErrInvalidRevision{`"@" statement is not valid, could be : <refname>@{push}, @{push}`}
                case TildePath, CaretPath, CaretReg:
                        if !hasReference {
                                return &ErrInvalidRevision{`"~" or "^" statement must have a reference defined at the beginning`}
                        }
                case ColonReg:
                        if len(*chunks) == 1 {
                                return nil
                        }

                        return &ErrInvalidRevision{`":" statement is not valid, could be : :/<regexp>`}
                case ColonPath:
                        if i == len(*chunks)-1 && hasReference || len(*chunks) == 1 {
                                return nil
                        }

                        return &ErrInvalidRevision{`":" statement is not valid, could be : <revision>:<path>`}
                case ColonStagePath:
                        if len(*chunks) == 1 {
                                return nil
                        }

                        return &ErrInvalidRevision{`":" statement is not valid, could be : :<n>:<path>`}
                }
        }

        return nil
}

// parseAt extract @ statements
func (p *Parser) parseAt() (Revisioner, error) {
        var tok, nextTok token
        var lit, nextLit string
        var err error

        tok, _, err = p.scan()

        if err != nil {
                return nil, err
        }

        if tok != obrace {
                p.unscan()

                return Ref("HEAD"), nil
        }

        tok, lit, err = p.scan()

        if err != nil {
                return nil, err
        }

        nextTok, nextLit, err = p.scan()

        if err != nil {
                return nil, err
        }

        switch {
        case tok == word && (lit == "u" || lit == "upstream") && nextTok == cbrace:
                return AtUpstream{}, nil
        case tok == word && lit == "push" && nextTok == cbrace:
                return AtPush{}, nil
        case tok == number && nextTok == cbrace:
                n, _ := strconv.Atoi(lit)

                return AtReflog{n}, nil
        case tok == minus && nextTok == number:
                n, _ := strconv.Atoi(nextLit)

                t, _, err := p.scan()

                if err != nil {
                        return nil, err
                }

                if t != cbrace {
                        return nil, &ErrInvalidRevision{s: `missing "}" in @{-n} structure`}
                }

                return AtCheckout{n}, nil
        default:
                p.unscan()

                date := lit

                for {
                        tok, lit, err = p.scan()

                        if err != nil {
                                return nil, err
                        }

                        switch {
                        case tok == cbrace:
                                t, err := time.Parse("2006-01-02T15:04:05Z", date)

                                if err != nil {
                                        return nil, &ErrInvalidRevision{fmt.Sprintf(`wrong date "%s" must fit ISO-8601 format : 2006-01-02T15:04:05Z`, date)}
                                }

                                return AtDate{t}, nil
                        case tok == eof:
                                return nil, &ErrInvalidRevision{s: `missing "}" in @{<data>} structure`}
                        default:
                                date += lit
                        }
                }
        }
}

// parseTilde extract ~ statements
func (p *Parser) parseTilde() (Revisioner, error) {
        var tok token
        var lit string
        var err error

        tok, lit, err = p.scan()

        if err != nil {
                return nil, err
        }

        switch {
        case tok == number:
                n, _ := strconv.Atoi(lit)

                return TildePath{n}, nil
        default:
                p.unscan()
                return TildePath{1}, nil
        }
}

// parseCaret extract ^ statements
func (p *Parser) parseCaret() (Revisioner, error) {
        var tok token
        var lit string
        var err error

        tok, lit, err = p.scan()

        if err != nil {
                return nil, err
        }

        switch {
        case tok == obrace:
                r, err := p.parseCaretBraces()

                if err != nil {
                        return nil, err
                }

                return r, nil
        case tok == number:
                n, _ := strconv.Atoi(lit)

                if n > 2 {
                        return nil, &ErrInvalidRevision{fmt.Sprintf(`"%s" found must be 0, 1 or 2 after "^"`, lit)}
                }

                return CaretPath{n}, nil
        default:
                p.unscan()
                return CaretPath{1}, nil
        }
}

// parseCaretBraces extract ^{<data>} statements
func (p *Parser) parseCaretBraces() (Revisioner, error) {
        var tok, nextTok token
        var lit, _ string
        start := true
        var re string
        var negate bool
        var err error

        for {
                tok, lit, err = p.scan()

                if err != nil {
                        return nil, err
                }

                nextTok, _, err = p.scan()

                if err != nil {
                        return nil, err
                }

                switch {
                case tok == word && nextTok == cbrace && (lit == "commit" || lit == "tree" || lit == "blob" || lit == "tag" || lit == "object"):
                        return CaretType{lit}, nil
                case re == "" && tok == cbrace:
                        return CaretType{"tag"}, nil
                case re == "" && tok == emark && nextTok == emark:
                        re += lit
                case re == "" && tok == emark && nextTok == minus:
                        negate = true
                case re == "" && tok == emark:
                        return nil, &ErrInvalidRevision{s: `revision suffix brace component sequences starting with "/!" others than those defined are reserved`}
                case re == "" && tok == slash:
                        p.unscan()
                case tok != slash && start:
                        return nil, &ErrInvalidRevision{fmt.Sprintf(`"%s" is not a valid revision suffix brace component`, lit)}
                case tok == eof:
                        return nil, &ErrInvalidRevision{s: `missing "}" in ^{<data>} structure`}
                case tok != cbrace:
                        p.unscan()
                        re += lit
                case tok == cbrace:
                        p.unscan()

                        reg, err := regexp.Compile(re)

                        if err != nil {
                                return CaretReg{}, &ErrInvalidRevision{fmt.Sprintf(`revision suffix brace component, %s`, err.Error())}
                        }

                        return CaretReg{reg, negate}, nil
                }

                start = false
        }
}

// parseColon extract : statements
func (p *Parser) parseColon() (Revisioner, error) {
        var tok token
        var err error

        tok, _, err = p.scan()

        if err != nil {
                return nil, err
        }

        switch tok {
        case slash:
                return p.parseColonSlash()
        default:
                p.unscan()
                return p.parseColonDefault()
        }
}

// parseColonSlash extract :/<data> statements
func (p *Parser) parseColonSlash() (Revisioner, error) {
        var tok, nextTok token
        var lit string
        var re string
        var negate bool
        var err error

        for {
                tok, lit, err = p.scan()

                if err != nil {
                        return nil, err
                }

                nextTok, _, err = p.scan()

                if err != nil {
                        return nil, err
                }

                switch {
                case tok == emark && nextTok == emark:
                        re += lit
                case re == "" && tok == emark && nextTok == minus:
                        negate = true
                case re == "" && tok == emark:
                        return nil, &ErrInvalidRevision{s: `revision suffix brace component sequences starting with "/!" others than those defined are reserved`}
                case tok == eof:
                        p.unscan()
                        reg, err := regexp.Compile(re)

                        if err != nil {
                                return ColonReg{}, &ErrInvalidRevision{fmt.Sprintf(`revision suffix brace component, %s`, err.Error())}
                        }

                        return ColonReg{reg, negate}, nil
                default:
                        p.unscan()
                        re += lit
                }
        }
}

// parseColonDefault extract :<data> statements
func (p *Parser) parseColonDefault() (Revisioner, error) {
        var tok token
        var lit string
        var path string
        var stage int
        var err error
        var n = -1

        tok, lit, err = p.scan()

        if err != nil {
                return nil, err
        }

        nextTok, _, err := p.scan()

        if err != nil {
                return nil, err
        }

        if tok == number && nextTok == colon {
                n, _ = strconv.Atoi(lit)
        }

        switch n {
        case 0, 1, 2, 3:
                stage = n
        default:
                path += lit
                p.unscan()
        }

        for {
                tok, lit, err = p.scan()

                if err != nil {
                        return nil, err
                }

                switch {
                case tok == eof && n == -1:
                        return ColonPath{path}, nil
                case tok == eof:
                        return ColonStagePath{path, stage}, nil
                default:
                        path += lit
                }
        }
}

// parseRef extract reference name
func (p *Parser) parseRef() (Revisioner, error) {
        var tok, prevTok token
        var lit, buf string
        var endOfRef bool
        var err error

        for {
                tok, lit, err = p.scan()

                if err != nil {
                        return nil, err
                }

                switch tok {
                case eof, at, colon, tilde, caret:
                        endOfRef = true
                }

                err := p.checkRefFormat(tok, lit, prevTok, buf, endOfRef)

                if err != nil {
                        return "", err
                }

                if endOfRef {
                        p.unscan()
                        return Ref(buf), nil
                }

                buf += lit
                prevTok = tok
        }
}

// checkRefFormat ensure reference name follow rules defined here :
// https://git-scm.com/docs/git-check-ref-format
func (p *Parser) checkRefFormat(token token, literal string, previousToken token, buffer string, endOfRef bool) error {
        switch token {
        case aslash, space, control, qmark, asterisk, obracket:
                return &ErrInvalidRevision{fmt.Sprintf(`must not contains "%s"`, literal)}
        }

        switch {
        case (token == dot || token == slash) && buffer == "":
                return &ErrInvalidRevision{fmt.Sprintf(`must not start with "%s"`, literal)}
        case previousToken == slash && endOfRef:
                return &ErrInvalidRevision{`must not end with "/"`}
        case previousToken == dot && endOfRef:
                return &ErrInvalidRevision{`must not end with "."`}
        case token == dot && previousToken == slash:
                return &ErrInvalidRevision{`must not contains "/."`}
        case previousToken == dot && token == dot:
                return &ErrInvalidRevision{`must not contains ".."`}
        case previousToken == slash && token == slash:
                return &ErrInvalidRevision{`must not contains consecutively "/"`}
        case (token == slash || endOfRef) && len(buffer) > 4 && buffer[len(buffer)-5:] == ".lock":
                return &ErrInvalidRevision{"cannot end with .lock"}
        }

        return nil
}

package revision

import (
        "bufio"
        "io"
        "unicode"
)

// runeCategoryValidator takes a rune as input and
// validates it belongs to a rune category
type runeCategoryValidator func(r rune) bool

// tokenizeExpression aggregates a series of runes matching check predicate into a single
// string and provides given tokenType as token type
func tokenizeExpression(ch rune, tokenType token, check runeCategoryValidator, r *bufio.Reader) (token, string, error) {
        var data []rune
        data = append(data, ch)

        for {
                c, _, err := r.ReadRune()

                if c == zeroRune {
                        break
                }

                if err != nil {
                        return tokenError, "", err
                }

                if check(c) {
                        data = append(data, c)
                } else {
                        err := r.UnreadRune()

                        if err != nil {
                                return tokenError, "", err
                        }

                        return tokenType, string(data), nil
                }
        }

        return tokenType, string(data), nil
}

// maxRevisionLength holds the maximum length that will be parsed for a
// revision. Git itself doesn't enforce a max length, but rather leans on
// the OS to enforce it via its ARG_MAX.
const maxRevisionLength = 128 * 1024 // 128kb

var zeroRune = rune(0)

// scanner represents a lexical scanner.
type scanner struct {
        r *bufio.Reader
}

// newScanner returns a new instance of scanner.
func newScanner(r io.Reader) *scanner {
        return &scanner{r: bufio.NewReader(io.LimitReader(r, maxRevisionLength))}
}

// Scan extracts tokens and their strings counterpart
// from the reader
func (s *scanner) scan() (token, string, error) {
        ch, _, err := s.r.ReadRune()

        if err != nil && err != io.EOF {
                return tokenError, "", err
        }

        switch ch {
        case zeroRune:
                return eof, "", nil
        case ':':
                return colon, string(ch), nil
        case '~':
                return tilde, string(ch), nil
        case '^':
                return caret, string(ch), nil
        case '.':
                return dot, string(ch), nil
        case '/':
                return slash, string(ch), nil
        case '{':
                return obrace, string(ch), nil
        case '}':
                return cbrace, string(ch), nil
        case '-':
                return minus, string(ch), nil
        case '@':
                return at, string(ch), nil
        case '\\':
                return aslash, string(ch), nil
        case '?':
                return qmark, string(ch), nil
        case '*':
                return asterisk, string(ch), nil
        case '[':
                return obracket, string(ch), nil
        case '!':
                return emark, string(ch), nil
        }

        if unicode.IsSpace(ch) {
                return space, string(ch), nil
        }

        if unicode.IsControl(ch) {
                return control, string(ch), nil
        }

        if unicode.IsLetter(ch) {
                return tokenizeExpression(ch, word, unicode.IsLetter, s.r)
        }

        if unicode.IsNumber(ch) {
                return tokenizeExpression(ch, number, unicode.IsNumber, s.r)
        }

        return tokenError, string(ch), nil
}

package config

// New creates a new config instance.
func New() *Config {
        return &Config{}
}

// Config contains all the sections, comments and includes from a config file.
type Config struct {
        Comment  *Comment
        Sections Sections
        Includes Includes
}

// Includes is a list of Includes in a config file.
type Includes []*Include

// Include is a reference to an included config file.
type Include struct {
        Path   string
        Config *Config
}

// Comment string without the prefix '#' or ';'.
type Comment string

const (
        // NoSubsection token is passed to Config.Section and Config.SetSection to
        // represent the absence of a section.
        NoSubsection = ""
)

// Section returns a existing section with the given name or creates a new one.
func (c *Config) Section(name string) *Section {
        for i := len(c.Sections) - 1; i >= 0; i-- {
                s := c.Sections[i]
                if s.IsName(name) {
                        return s
                }
        }

        s := &Section{Name: name}
        c.Sections = append(c.Sections, s)
        return s
}

// HasSection checks if the Config has a section with the specified name.
func (c *Config) HasSection(name string) bool {
        for _, s := range c.Sections {
                if s.IsName(name) {
                        return true
                }
        }
        return false
}

// RemoveSection removes a section from a config file.
func (c *Config) RemoveSection(name string) *Config {
        result := Sections{}
        for _, s := range c.Sections {
                if !s.IsName(name) {
                        result = append(result, s)
                }
        }

        c.Sections = result
        return c
}

// RemoveSubsection remove a subsection from a config file.
func (c *Config) RemoveSubsection(section string, subsection string) *Config {
        for _, s := range c.Sections {
                if s.IsName(section) {
                        result := Subsections{}
                        for _, ss := range s.Subsections {
                                if !ss.IsName(subsection) {
                                        result = append(result, ss)
                                }
                        }
                        s.Subsections = result
                }
        }

        return c
}

// AddOption adds an option to a given section and subsection. Use the
// NoSubsection constant for the subsection argument if no subsection is wanted.
func (c *Config) AddOption(section string, subsection string, key string, value string) *Config {
        if subsection == "" {
                c.Section(section).AddOption(key, value)
        } else {
                c.Section(section).Subsection(subsection).AddOption(key, value)
        }

        return c
}

// SetOption sets an option to a given section and subsection. Use the
// NoSubsection constant for the subsection argument if no subsection is wanted.
func (c *Config) SetOption(section string, subsection string, key string, value string) *Config {
        if subsection == "" {
                c.Section(section).SetOption(key, value)
        } else {
                c.Section(section).Subsection(subsection).SetOption(key, value)
        }

        return c
}

package config

import (
        "io"

        "github.com/go-git/gcfg/v2"
)

// A Decoder reads and decodes config files from an input stream.
type Decoder struct {
        io.Reader
}

// NewDecoder returns a new decoder that reads from r.
func NewDecoder(r io.Reader) *Decoder {
        return &Decoder{r}
}

// Decode reads the whole config from its input and stores it in the
// value pointed to by config.
func (d *Decoder) Decode(config *Config) error {
        cb := func(s string, ss string, k string, v string, bv bool) error {
                if ss == "" && k == "" {
                        config.Section(s)
                        return nil
                }

                if ss != "" && k == "" {
                        config.Section(s).Subsection(ss)
                        return nil
                }

                config.AddOption(s, ss, k, v)
                return nil
        }
        return gcfg.ReadWithCallback(d, cb)
}

package config

import (
        "fmt"
        "io"
        "strings"
)

// An Encoder writes config files to an output stream.
type Encoder struct {
        w io.Writer
}

var (
        subsectionReplacer = strings.NewReplacer(`"`, `\"`, `\`, `\\`)
        valueReplacer = strings.NewReplacer(`"`, `\"`, `\`, `\\`, "\n", `\n`, "\t", `\t`, "\b", `\b`)
)
// NewEncoder returns a new encoder that writes to w.
func NewEncoder(w io.Writer) *Encoder {
        return &Encoder{w}
}

// Encode writes the config in git config format to the stream of the encoder.
func (e *Encoder) Encode(cfg *Config) error {
        for _, s := range cfg.Sections {
                if err := e.encodeSection(s); err != nil {
                        return err
                }
        }

        return nil
}

func (e *Encoder) encodeSection(s *Section) error {
        if len(s.Options) > 0 {
                if err := e.printf("[%s]\n", s.Name); err != nil {
                        return err
                }

                if err := e.encodeOptions(s.Options); err != nil {
                        return err
                }
        }

        for _, ss := range s.Subsections {
                if err := e.encodeSubsection(s.Name, ss); err != nil {
                        return err
                }
        }

        return nil
}

func (e *Encoder) encodeSubsection(sectionName string, s *Subsection) error {
        if err := e.printf("[%s \"%s\"]\n", sectionName, subsectionReplacer.Replace(s.Name)); err != nil {
                return err
        }

        return e.encodeOptions(s.Options)
}

func (e *Encoder) encodeOptions(opts Options) error {
        for _, o := range opts {
                var value string
                if strings.ContainsAny(o.Value, "#;\"\t\n\\") || strings.HasPrefix(o.Value, " ") || strings.HasSuffix(o.Value, " ") {
                        value = `"`+valueReplacer.Replace(o.Value)+`"`
                } else {
                        value = o.Value
                }

                if err := e.printf("\t%s = %s\n", o.Key, value); err != nil {
                        return err
                }
        }

        return nil
}

func (e *Encoder) printf(msg string, args ...interface{}) error {
        _, err := fmt.Fprintf(e.w, msg, args...)
        return err
}

package config

import "errors"

// RepositoryFormatVersion represents the repository format version,
// as per defined at:
//
//        https://git-scm.com/docs/repository-version
type RepositoryFormatVersion string

const (
        // Version_0 is the format defined by the initial version of git,
        // including but not limited to the format of the repository
        // directory, the repository configuration file, and the object
        // and ref storage.
        //
        // Specifying the complete behavior of git is beyond the scope
        // of this document.
        Version_0 = "0"

        // Version_1 is identical to version 0, with the following exceptions:
        //
        //   1. When reading the core.repositoryformatversion variable, a git
        //                implementation which supports version 1 MUST also read any
        //                configuration keys found in the extensions section of the
        //                configuration file.
        //
        //         2. If a version-1 repository specifies any extensions.* keys that
        //                the running git has not implemented, the operation MUST NOT proceed.
        //                Similarly, if the value of any known key is not understood by the
        //                implementation, the operation MUST NOT proceed.
        //
        // Note that if no extensions are specified in the config file, then
        // core.repositoryformatversion SHOULD be set to 0 (setting it to 1 provides
        // no benefit, and makes the repository incompatible with older
        // implementations of git).
        Version_1 = "1"

        // DefaultRepositoryFormatVersion holds the default repository format version.
        DefaultRepositoryFormatVersion = Version_0
)

// ObjectFormat defines the object format.
type ObjectFormat int

const (
        // SHA1 represents the object format used for SHA1.
        SHA1 ObjectFormat = iota

        // SHA256 represents the object format used for SHA256.
        SHA256

        // DefaultObjectFormat holds the default object format.
        DefaultObjectFormat = SHA1
)

// String returns the string representation of the ObjectFormat.
func (f ObjectFormat) String() string {
        switch f {
        case SHA1:
                return "sha1"
        case SHA256:
                return "sha256"
        default:
                return ""
        }
}

// Size returns the hash size of the ObjectFormat.
func (f ObjectFormat) Size() int {
        switch f {
        case SHA1:
                return SHA1Size
        case SHA256:
                return SHA256Size
        default:
                return 0
        }
}

// HexSize returns the hash size in hexadecimal format of the ObjectFormat.
func (f ObjectFormat) HexSize() int {
        switch f {
        case SHA1:
                return SHA1HexSize
        case SHA256:
                return SHA256HexSize
        default:
                return 0
        }
}

// ErrInvalidObjectFormat is returned when an invalid ObjectFormat is used.
var ErrInvalidObjectFormat = errors.New("invalid object format")

const (
        // SHA1Size is the size of SHA1 hash.
        SHA1Size = 20
        // SHA256Size is the size of SHA256 hash.
        SHA256Size = 32
        // SHA1HexSize is the size of SHA1 hash in hexadecimal format.
        SHA1HexSize = SHA1Size * 2
        // SHA256HexSize is the size of SHA256 hash in hexadecimal format.
        SHA256HexSize = SHA256Size * 2
)

package config

import (
        "fmt"
        "strings"
)

// Option defines a key/value entity in a config file.
type Option struct {
        // Key preserving original caseness.
        // Use IsKey instead to compare key regardless of caseness.
        Key string
        // Original value as string, could be not normalized.
        Value string
}

type Options []*Option

// IsKey returns true if the given key matches
// this option's key in a case-insensitive comparison.
func (o *Option) IsKey(key string) bool {
        return strings.EqualFold(o.Key, key)
}

func (opts Options) GoString() string {
        var strs []string
        for _, opt := range opts {
                strs = append(strs, fmt.Sprintf("%#v", opt))
        }

        return strings.Join(strs, ", ")
}

// Get gets the value for the given key if set,
// otherwise it returns the empty string.
//
// Note that there is no difference
//
// This matches git behaviour since git v1.8.1-rc1,
// if there are multiple definitions of a key, the
// last one wins.
//
// See: http://article.gmane.org/gmane.linux.kernel/1407184
//
// In order to get all possible values for the same key,
// use GetAll.
func (opts Options) Get(key string) string {
        for i := len(opts) - 1; i >= 0; i-- {
                o := opts[i]
                if o.IsKey(key) {
                        return o.Value
                }
        }
        return ""
}

// Has checks if an Option exist with the given key.
func (opts Options) Has(key string) bool {
        for _, o := range opts {
                if o.IsKey(key) {
                        return true
                }
        }
        return false
}

// GetAll returns all possible values for the same key.
func (opts Options) GetAll(key string) []string {
        result := []string{}
        for _, o := range opts {
                if o.IsKey(key) {
                        result = append(result, o.Value)
                }
        }
        return result
}

func (opts Options) withoutOption(key string) Options {
        result := Options{}
        for _, o := range opts {
                if !o.IsKey(key) {
                        result = append(result, o)
                }
        }
        return result
}

func (opts Options) withAddedOption(key string, value string) Options {
        return append(opts, &Option{key, value})
}

func (opts Options) withSettedOption(key string, values ...string) Options {
        var result Options
        var added []string
        for _, o := range opts {
                if !o.IsKey(key) {
                        result = append(result, o)
                        continue
                }

                if contains(values, o.Value) {
                        added = append(added, o.Value)
                        result = append(result, o)
                        continue
                }
        }

        for _, value := range values {
                if contains(added, value) {
                        continue
                }

                result = result.withAddedOption(key, value)
        }

        return result
}

func contains(haystack []string, needle string) bool {
        for _, s := range haystack {
                if s == needle {
                        return true
                }
        }

        return false
}

package config

import (
        "fmt"
        "strings"
)

// Section is the representation of a section inside git configuration files.
// Each Section contains Options that are used by both the Git plumbing
// and the porcelains.
// Sections can be further divided into subsections. To begin a subsection
// put its name in double quotes, separated by space from the section name,
// in the section header, like in the example below:
//
//     [section "subsection"]
//
// All the other lines (and the remainder of the line after the section header)
// are recognized as option variables, in the form "name = value" (or just name,
// which is a short-hand to say that the variable is the boolean "true").
// The variable names are case-insensitive, allow only alphanumeric characters
// and -, and must start with an alphabetic character:
//
//     [section "subsection1"]
//         option1 = value1
//         option2
//     [section "subsection2"]
//         option3 = value2
//
type Section struct {
        Name        string
        Options     Options
        Subsections Subsections
}

type Subsection struct {
        Name    string
        Options Options
}

type Sections []*Section

func (s Sections) GoString() string {
        var strs []string
        for _, ss := range s {
                strs = append(strs, fmt.Sprintf("%#v", ss))
        }

        return strings.Join(strs, ", ")
}

type Subsections []*Subsection

func (s Subsections) GoString() string {
        var strs []string
        for _, ss := range s {
                strs = append(strs, fmt.Sprintf("%#v", ss))
        }

        return strings.Join(strs, ", ")
}

// IsName checks if the name provided is equals to the Section name, case insensitive.
func (s *Section) IsName(name string) bool {
        return strings.EqualFold(s.Name, name)
}

// Subsection returns a Subsection from the specified Section. If the
// Subsection does not exists, new one is created and added to Section.
func (s *Section) Subsection(name string) *Subsection {
        for i := len(s.Subsections) - 1; i >= 0; i-- {
                ss := s.Subsections[i]
                if ss.IsName(name) {
                        return ss
                }
        }

        ss := &Subsection{Name: name}
        s.Subsections = append(s.Subsections, ss)
        return ss
}

// HasSubsection checks if the Section has a Subsection with the specified name.
func (s *Section) HasSubsection(name string) bool {
        for _, ss := range s.Subsections {
                if ss.IsName(name) {
                        return true
                }
        }

        return false
}

// RemoveSubsection removes a subsection from a Section.
func (s *Section) RemoveSubsection(name string) *Section {
        result := Subsections{}
        for _, s := range s.Subsections {
                if !s.IsName(name) {
                        result = append(result, s)
                }
        }

        s.Subsections = result
        return s
}

// Option returns the value for the specified key. Empty string is returned if
// key does not exists.
func (s *Section) Option(key string) string {
        return s.Options.Get(key)
}

// OptionAll returns all possible values for an option with the specified key.
// If the option does not exists, an empty slice will be returned.
func (s *Section) OptionAll(key string) []string {
        return s.Options.GetAll(key)
}

// HasOption checks if the Section has an Option with the given key.
func (s *Section) HasOption(key string) bool {
        return s.Options.Has(key)
}

// AddOption adds a new Option to the Section. The updated Section is returned.
func (s *Section) AddOption(key string, value string) *Section {
        s.Options = s.Options.withAddedOption(key, value)
        return s
}

// SetOption adds a new Option to the Section. If the option already exists, is replaced.
// The updated Section is returned.
func (s *Section) SetOption(key string, value string) *Section {
        s.Options = s.Options.withSettedOption(key, value)
        return s
}

// Remove an option with the specified key. The updated Section is returned.
func (s *Section) RemoveOption(key string) *Section {
        s.Options = s.Options.withoutOption(key)
        return s
}

// IsName checks if the name of the subsection is exactly the specified name.
func (s *Subsection) IsName(name string) bool {
        return s.Name == name
}

// Option returns an option with the specified key. If the option does not exists,
// empty spring will be returned.
func (s *Subsection) Option(key string) string {
        return s.Options.Get(key)
}

// OptionAll returns all possible values for an option with the specified key.
// If the option does not exists, an empty slice will be returned.
func (s *Subsection) OptionAll(key string) []string {
        return s.Options.GetAll(key)
}

// HasOption checks if the Subsection has an Option with the given key.
func (s *Subsection) HasOption(key string) bool {
        return s.Options.Has(key)
}

// AddOption adds a new Option to the Subsection. The updated Subsection is returned.
func (s *Subsection) AddOption(key string, value string) *Subsection {
        s.Options = s.Options.withAddedOption(key, value)
        return s
}

// SetOption adds a new Option to the Subsection. If the option already exists, is replaced.
// The updated Subsection is returned.
func (s *Subsection) SetOption(key string, value ...string) *Subsection {
        s.Options = s.Options.withSettedOption(key, value...)
        return s
}

// RemoveOption removes the option with the specified key. The updated Subsection is returned.
func (s *Subsection) RemoveOption(key string) *Subsection {
        s.Options = s.Options.withoutOption(key)
        return s
}

package packfile

import (
        "io"
        "time"

        "github.com/go-git/go-git/v6/plumbing/storer"
        "github.com/go-git/go-git/v6/utils/ioutil"
        "github.com/go-git/go-git/v6/utils/sync"
        "github.com/go-git/go-git/v6/utils/trace"
)

var signature = []byte{'P', 'A', 'C', 'K'}

const (
        // VersionSupported is the packfile version supported by this package
        VersionSupported uint32 = 2

        firstLengthBits = uint8(4)   // the first byte into object header has 4 bits to store the length
        lengthBits      = uint8(7)   // subsequent bytes has 7 bits to store the length
        maskFirstLength = 15         // 0000 1111
        maskContinue    = 0x80       // 1000 0000
        maskLength      = uint8(127) // 0111 1111
        maskType        = uint8(112) // 0111 0000
)

// UpdateObjectStorage updates the storer with the objects in the given
// packfile.
func UpdateObjectStorage(s storer.Storer, packfile io.Reader) error {
        start := time.Now()
        defer func() {
                trace.Performance.Printf("performance: %.9f s: update_obj_storage", time.Since(start).Seconds())
        }()

        if pw, ok := s.(storer.PackfileWriter); ok {
                return WritePackfileToObjectStorage(pw, packfile)
        }

        p := NewParser(packfile, WithStorage(s))

        _, err := p.Parse()
        return err
}

// WritePackfileToObjectStorage writes all the packfile objects into the given
// object storage.
func WritePackfileToObjectStorage(
        sw storer.PackfileWriter,
        packfile io.Reader,
) (err error) {
        w, err := sw.PackfileWriter()
        if err != nil {
                return err
        }

        defer ioutil.CheckClose(w, &err)
        var n int64

        buf := sync.GetByteSlice()
        n, err = io.CopyBuffer(w, packfile, *buf)
        sync.PutByteSlice(buf)

        if err == nil && n == 0 {
                return ErrEmptyPackfile
        }

        return err
}

package packfile

const blksz = 16
const maxChainLength = 64

// deltaIndex is a modified version of JGit's DeltaIndex adapted to our current
// design.
type deltaIndex struct {
        table   []int
        entries []int
        mask    int
}

func (idx *deltaIndex) init(buf []byte) {
        scanner := newDeltaIndexScanner(buf, len(buf))
        idx.mask = scanner.mask
        idx.table = scanner.table
        idx.entries = make([]int, countEntries(scanner)+1)
        idx.copyEntries(scanner)
}

// findMatch returns the offset of src where the block starting at tgtOffset
// is and the length of the match. A length of 0 means there was no match. A
// length of -1 means the src length is lower than the blksz and whatever
// other positive length is the length of the match in bytes.
func (idx *deltaIndex) findMatch(src, tgt []byte, tgtOffset int) (srcOffset, l int) {
        if len(tgt) < tgtOffset+s {
                return 0, len(tgt) - tgtOffset
        }

        if len(src) < blksz {
                return 0, -1
        }

        h := hashBlock(tgt, tgtOffset)
        tIdx := h & idx.mask
        eIdx := idx.table[tIdx]
        if eIdx == 0 {
                return
        }

        srcOffset = idx.entries[eIdx]

        l = matchLength(src, tgt, tgtOffset, srcOffset)

        return
}

func matchLength(src, tgt []byte, otgt, osrc int) (l int) {
        lensrc := len(src)
        lentgt := len(tgt)
        for (osrc < lensrc && otgt < lentgt) && src[osrc] == tgt[otgt] {
                l++
                osrc++
                otgt++
        }
        return
}

func countEntries(scan *deltaIndexScanner) (cnt int) {
        // Figure out exactly how many entries we need. As we do the
        // enumeration truncate any delta chains longer than what we
        // are willing to scan during encode. This keeps the encode
        // logic linear in the size of the input rather than quadratic.
        for i := 0; i < len(scan.table); i++ {
                h := scan.table[i]
                if h == 0 {
                        continue
                }

                size := 0
                for {
                        size++
                        if size == maxChainLength {
                                scan.next[h] = 0
                                break
                        }
                        h = scan.next[h]

                        if h == 0 {
                                break
                        }
                }
                cnt += size
        }

        return
}

func (idx *deltaIndex) copyEntries(scanner *deltaIndexScanner) {
        // Rebuild the entries list from the scanner, positioning all
        // blocks in the same hash chain next to each other. We can
        // then later discard the next list, along with the scanner.
        //
        next := 1
        for i := 0; i < len(idx.table); i++ {
                h := idx.table[i]
                if h == 0 {
                        continue
                }

                idx.table[i] = next
                for {
                        idx.entries[next] = scanner.entries[h]
                        next++
                        h = scanner.next[h]

                        if h == 0 {
                                break
                        }
                }
        }
}

type deltaIndexScanner struct {
        table   []int
        entries []int
        next    []int
        mask    int
        count   int
}

func newDeltaIndexScanner(buf []byte, size int) *deltaIndexScanner {
        size -= size % blksz
        worstCaseBlockCnt := size / blksz
        if worstCaseBlockCnt < 1 {
                return new(deltaIndexScanner)
        }

        tableSize := tableSize(worstCaseBlockCnt)
        scanner := &deltaIndexScanner{
                table:   make([]int, tableSize),
                mask:    tableSize - 1,
                entries: make([]int, worstCaseBlockCnt+1),
                next:    make([]int, worstCaseBlockCnt+1),
        }

        scanner.scan(buf, size)
        return scanner
}

// slightly modified version of JGit's DeltaIndexScanner. We store the offset on the entries
// instead of the entries and the key, so we avoid operations to retrieve the offset later, as
// we don't use the key.
// See: https://github.com/eclipse/jgit/blob/005e5feb4ecd08c4e4d141a38b9e7942accb3212/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/pack/DeltaIndexScanner.java
func (s *deltaIndexScanner) scan(buf []byte, end int) {
        lastHash := 0
        ptr := end - blksz

        for {
                key := hashBlock(buf, ptr)
                tIdx := key & s.mask
                head := s.table[tIdx]
                if head != 0 && lastHash == key {
                        s.entries[head] = ptr
                } else {
                        s.count++
                        eIdx := s.count
                        s.entries[eIdx] = ptr
                        s.next[eIdx] = head
                        s.table[tIdx] = eIdx
                }

                lastHash = key
                ptr -= blksz

                if 0 > ptr {
                        break
                }
        }
}

func tableSize(worstCaseBlockCnt int) int {
        shift := 32 - leadingZeros(uint32(worstCaseBlockCnt))
        sz := 1 << uint(shift-1)
        if sz < worstCaseBlockCnt {
                sz <<= 1
        }
        return sz
}

// use https://golang.org/pkg/math/bits/#LeadingZeros32 in the future
func leadingZeros(x uint32) (n int) {
        if x >= 1<<16 {
                x >>= 16
                n = 16
        }
        if x >= 1<<8 {
                x >>= 8
                n += 8
        }
        n += int(len8tab[x])
        return 32 - n
}

var len8tab = [256]uint8{
        0x00, 0x01, 0x02, 0x02, 0x03, 0x03, 0x03, 0x03, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
        0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05,
        0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06,
        0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06,
        0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
        0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
        0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
        0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
        0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
        0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
        0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
        0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
        0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
        0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
        0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
        0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
}

func hashBlock(raw []byte, ptr int) int {
        // The first 4 steps collapse out into a 4 byte big-endian decode,
        // with a larger right shift as we combined shift lefts together.
        //
        hash := ((uint32(raw[ptr]) & 0xff) << 24) |
                ((uint32(raw[ptr+1]) & 0xff) << 16) |
                ((uint32(raw[ptr+2]) & 0xff) << 8) |
                (uint32(raw[ptr+3]) & 0xff)
        hash ^= T[hash>>31]

        hash = ((hash << 8) | (uint32(raw[ptr+4]) & 0xff)) ^ T[hash>>23]
        hash = ((hash << 8) | (uint32(raw[ptr+5]) & 0xff)) ^ T[hash>>23]
        hash = ((hash << 8) | (uint32(raw[ptr+6]) & 0xff)) ^ T[hash>>23]
        hash = ((hash << 8) | (uint32(raw[ptr+7]) & 0xff)) ^ T[hash>>23]

        hash = ((hash << 8) | (uint32(raw[ptr+8]) & 0xff)) ^ T[hash>>23]
        hash = ((hash << 8) | (uint32(raw[ptr+9]) & 0xff)) ^ T[hash>>23]
        hash = ((hash << 8) | (uint32(raw[ptr+10]) & 0xff)) ^ T[hash>>23]
        hash = ((hash << 8) | (uint32(raw[ptr+11]) & 0xff)) ^ T[hash>>23]

        hash = ((hash << 8) | (uint32(raw[ptr+12]) & 0xff)) ^ T[hash>>23]
        hash = ((hash << 8) | (uint32(raw[ptr+13]) & 0xff)) ^ T[hash>>23]
        hash = ((hash << 8) | (uint32(raw[ptr+14]) & 0xff)) ^ T[hash>>23]
        hash = ((hash << 8) | (uint32(raw[ptr+15]) & 0xff)) ^ T[hash>>23]

        return int(hash)
}

var T = []uint32{0x00000000, 0xd4c6b32d, 0x7d4bd577,
        0xa98d665a, 0x2e5119c3, 0xfa97aaee, 0x531accb4, 0x87dc7f99,
        0x5ca23386, 0x886480ab, 0x21e9e6f1, 0xf52f55dc, 0x72f32a45,
        0xa6359968, 0x0fb8ff32, 0xdb7e4c1f, 0x6d82d421, 0xb944670c,
        0x10c90156, 0xc40fb27b, 0x43d3cde2, 0x97157ecf, 0x3e981895,
        0xea5eabb8, 0x3120e7a7, 0xe5e6548a, 0x4c6b32d0, 0x98ad81fd,
        0x1f71fe64, 0xcbb74d49, 0x623a2b13, 0xb6fc983e, 0x0fc31b6f,
        0xdb05a842, 0x7288ce18, 0xa64e7d35, 0x219202ac, 0xf554b181,
        0x5cd9d7db, 0x881f64f6, 0x536128e9, 0x87a79bc4, 0x2e2afd9e,
        0xfaec4eb3, 0x7d30312a, 0xa9f68207, 0x007be45d, 0xd4bd5770,
        0x6241cf4e, 0xb6877c63, 0x1f0a1a39, 0xcbcca914, 0x4c10d68d,
        0x98d665a0, 0x315b03fa, 0xe59db0d7, 0x3ee3fcc8, 0xea254fe5,
        0x43a829bf, 0x976e9a92, 0x10b2e50b, 0xc4745626, 0x6df9307c,
        0xb93f8351, 0x1f8636de, 0xcb4085f3, 0x62cde3a9, 0xb60b5084,
        0x31d72f1d, 0xe5119c30, 0x4c9cfa6a, 0x985a4947, 0x43240558,
        0x97e2b675, 0x3e6fd02f, 0xeaa96302, 0x6d751c9b, 0xb9b3afb6,
        0x103ec9ec, 0xc4f87ac1, 0x7204e2ff, 0xa6c251d2, 0x0f4f3788,
        0xdb8984a5, 0x5c55fb3c, 0x88934811, 0x211e2e4b, 0xf5d89d66,
        0x2ea6d179, 0xfa606254, 0x53ed040e, 0x872bb723, 0x00f7c8ba,
        0xd4317b97, 0x7dbc1dcd, 0xa97aaee0, 0x10452db1, 0xc4839e9c,
        0x6d0ef8c6, 0xb9c84beb, 0x3e143472, 0xead2875f, 0x435fe105,
        0x97995228, 0x4ce71e37, 0x9821ad1a, 0x31accb40, 0xe56a786d,
        0x62b607f4, 0xb670b4d9, 0x1ffdd283, 0xcb3b61ae, 0x7dc7f990,
        0xa9014abd, 0x008c2ce7, 0xd44a9fca, 0x5396e053, 0x8750537e,
        0x2edd3524, 0xfa1b8609, 0x2165ca16, 0xf5a3793b, 0x5c2e1f61,
        0x88e8ac4c, 0x0f34d3d5, 0xdbf260f8, 0x727f06a2, 0xa6b9b58f,
        0x3f0c6dbc, 0xebcade91, 0x4247b8cb, 0x96810be6, 0x115d747f,
        0xc59bc752, 0x6c16a108, 0xb8d01225, 0x63ae5e3a, 0xb768ed17,
        0x1ee58b4d, 0xca233860, 0x4dff47f9, 0x9939f4d4, 0x30b4928e,
        0xe47221a3, 0x528eb99d, 0x86480ab0, 0x2fc56cea, 0xfb03dfc7,
        0x7cdfa05e, 0xa8191373, 0x01947529, 0xd552c604, 0x0e2c8a1b,
        0xdaea3936, 0x73675f6c, 0xa7a1ec41, 0x207d93d8, 0xf4bb20f5,
        0x5d3646af, 0x89f0f582, 0x30cf76d3, 0xe409c5fe, 0x4d84a3a4,
        0x99421089, 0x1e9e6f10, 0xca58dc3d, 0x63d5ba67, 0xb713094a,
        0x6c6d4555, 0xb8abf678, 0x11269022, 0xc5e0230f, 0x423c5c96,
        0x96faefbb, 0x3f7789e1, 0xebb13acc, 0x5d4da2f2, 0x898b11df,
        0x20067785, 0xf4c0c4a8, 0x731cbb31, 0xa7da081c, 0x0e576e46,
        0xda91dd6b, 0x01ef9174, 0xd5292259, 0x7ca44403, 0xa862f72e,
        0x2fbe88b7, 0xfb783b9a, 0x52f55dc0, 0x8633eeed, 0x208a5b62,
        0xf44ce84f, 0x5dc18e15, 0x89073d38, 0x0edb42a1, 0xda1df18c,
        0x739097d6, 0xa75624fb, 0x7c2868e4, 0xa8eedbc9, 0x0163bd93,
        0xd5a50ebe, 0x52797127, 0x86bfc20a, 0x2f32a450, 0xfbf4177d,
        0x4d088f43, 0x99ce3c6e, 0x30435a34, 0xe485e919, 0x63599680,
        0xb79f25ad, 0x1e1243f7, 0xcad4f0da, 0x11aabcc5, 0xc56c0fe8,
        0x6ce169b2, 0xb827da9f, 0x3ffba506, 0xeb3d162b, 0x42b07071,
        0x9676c35c, 0x2f49400d, 0xfb8ff320, 0x5202957a, 0x86c42657,
        0x011859ce, 0xd5deeae3, 0x7c538cb9, 0xa8953f94, 0x73eb738b,
        0xa72dc0a6, 0x0ea0a6fc, 0xda6615d1, 0x5dba6a48, 0x897cd965,
        0x20f1bf3f, 0xf4370c12, 0x42cb942c, 0x960d2701, 0x3f80415b,
        0xeb46f276, 0x6c9a8def, 0xb85c3ec2, 0x11d15898, 0xc517ebb5,
        0x1e69a7aa, 0xcaaf1487, 0x632272dd, 0xb7e4c1f0, 0x3038be69,
        0xe4fe0d44, 0x4d736b1e, 0x99b5d833,
}

package packfile

import (
        "sort"
        "sync"

        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/storer"
)

const (
        // deltas based on deltas, how many steps we can do.
        // 50 is the default value used in JGit
        maxDepth = int64(50)
)

// applyDelta is the set of object types that we should apply deltas
var applyDelta = map[plumbing.ObjectType]bool{
        plumbing.BlobObject: true,
        plumbing.TreeObject: true,
}

type deltaSelector struct {
        storer storer.EncodedObjectStorer
}

func newDeltaSelector(s storer.EncodedObjectStorer) *deltaSelector {
        return &deltaSelector{s}
}

// ObjectsToPack creates a list of ObjectToPack from the hashes
// provided, creating deltas if it's suitable, using an specific
// internal logic.  `packWindow` specifies the size of the sliding
// window used to compare objects for delta compression; 0 turns off
// delta compression entirely.
func (dw *deltaSelector) ObjectsToPack(
        hashes []plumbing.Hash,
        packWindow uint,
) ([]*ObjectToPack, error) {
        otp, err := dw.objectsToPack(hashes, packWindow)
        if err != nil {
                return nil, err
        }

        if packWindow == 0 {
                return otp, nil
        }

        dw.sort(otp)

        var objectGroups [][]*ObjectToPack
        var prev *ObjectToPack
        i := -1
        for _, obj := range otp {
                if prev == nil || prev.Type() != obj.Type() {
                        objectGroups = append(objectGroups, []*ObjectToPack{obj})
                        i++
                        prev = obj
                } else {
                        objectGroups[i] = append(objectGroups[i], obj)
                }
        }

        var wg sync.WaitGroup
        var once sync.Once
        for _, objs := range objectGroups {
                objs := objs
                wg.Add(1)
                go func() {
                        if walkErr := dw.walk(objs, packWindow); walkErr != nil {
                                once.Do(func() {
                                        err = walkErr
                                })
                        }
                        wg.Done()
                }()
        }
        wg.Wait()

        if err != nil {
                return nil, err
        }

        return otp, nil
}

func (dw *deltaSelector) objectsToPack(
        hashes []plumbing.Hash,
        packWindow uint,
) ([]*ObjectToPack, error) {
        var objectsToPack []*ObjectToPack
        for _, h := range hashes {
                var o plumbing.EncodedObject
                var err error
                if packWindow == 0 {
                        o, err = dw.encodedObject(h)
                } else {
                        o, err = dw.encodedDeltaObject(h)
                }
                if err != nil {
                        return nil, err
                }

                otp := newObjectToPack(o)
                if _, ok := o.(plumbing.DeltaObject); ok {
                        otp.CleanOriginal()
                }

                objectsToPack = append(objectsToPack, otp)
        }

        if packWindow == 0 {
                return objectsToPack, nil
        }

        if err := dw.fixAndBreakChains(objectsToPack); err != nil {
                return nil, err
        }

        return objectsToPack, nil
}

func (dw *deltaSelector) encodedDeltaObject(h plumbing.Hash) (plumbing.EncodedObject, error) {
        edos, ok := dw.storer.(storer.DeltaObjectStorer)
        if !ok {
                return dw.encodedObject(h)
        }

        return edos.DeltaObject(plumbing.AnyObject, h)
}

func (dw *deltaSelector) encodedObject(h plumbing.Hash) (plumbing.EncodedObject, error) {
        return dw.storer.EncodedObject(plumbing.AnyObject, h)
}

func (dw *deltaSelector) fixAndBreakChains(objectsToPack []*ObjectToPack) error {
        m := make(map[plumbing.Hash]*ObjectToPack, len(objectsToPack))
        for _, otp := range objectsToPack {
                m[otp.Hash()] = otp
        }

        for _, otp := range objectsToPack {
                if err := dw.fixAndBreakChainsOne(m, otp); err != nil {
                        return err
                }
        }

        return nil
}

func (dw *deltaSelector) fixAndBreakChainsOne(objectsToPack map[plumbing.Hash]*ObjectToPack, otp *ObjectToPack) error {
        if !otp.Object.Type().IsDelta() {
                return nil
        }

        // Initial ObjectToPack instances might have a delta assigned to Object
        // but no actual base initially. Once Base is assigned to a delta, it means
        // we already fixed it.
        if otp.Base != nil {
                return nil
        }

        do, ok := otp.Object.(plumbing.DeltaObject)
        if !ok {
                // if this is not a DeltaObject, then we cannot retrieve its base,
                // so we have to break the delta chain here.
                return dw.undeltify(otp)
        }

        base, ok := objectsToPack[do.BaseHash()]
        if !ok {
                // The base of the delta is not in our list of objects to pack, so
                // we break the chain.
                return dw.undeltify(otp)
        }

        if err := dw.fixAndBreakChainsOne(objectsToPack, base); err != nil {
                return err
        }

        otp.SetDelta(base, otp.Object)
        return nil
}

func (dw *deltaSelector) restoreOriginal(otp *ObjectToPack) error {
        if otp.Original != nil {
                return nil
        }

        if !otp.Object.Type().IsDelta() {
                return nil
        }

        obj, err := dw.encodedObject(otp.Hash())
        if err != nil {
                return err
        }

        otp.SetOriginal(obj)

        return nil
}

// undeltify undeltifies an *ObjectToPack by retrieving the original object from
// the storer and resetting it.
func (dw *deltaSelector) undeltify(otp *ObjectToPack) error {
        if err := dw.restoreOriginal(otp); err != nil {
                return err
        }

        otp.Object = otp.Original
        otp.Depth = 0
        return nil
}

func (dw *deltaSelector) sort(objectsToPack []*ObjectToPack) {
        sort.Sort(byTypeAndSize(objectsToPack))
}

func (dw *deltaSelector) walk(
        objectsToPack []*ObjectToPack,
        packWindow uint,
) error {
        indexMap := make(map[plumbing.Hash]*deltaIndex)
        for i := 0; i < len(objectsToPack); i++ {
                // Clean up the index map and reconstructed delta objects for anything
                // outside our pack window, to save memory.
                if i > int(packWindow) {
                        obj := objectsToPack[i-int(packWindow)]

                        delete(indexMap, obj.Hash())

                        if obj.IsDelta() {
                                obj.SaveOriginalMetadata()
                                obj.CleanOriginal()
                        }
                }

                target := objectsToPack[i]

                // If we already have a delta, we don't try to find a new one for this
                // object. This happens when a delta is set to be reused from an existing
                // packfile.
                if target.IsDelta() {
                        continue
                }

                // We only want to create deltas from specific types.
                if !applyDelta[target.Type()] {
                        continue
                }

                for j := i - 1; j >= 0 && i-j < int(packWindow); j-- {
                        base := objectsToPack[j]
                        // Objects must use only the same type as their delta base.
                        // Since objectsToPack is sorted by type and size, once we find
                        // a different type, we know we won't find more of them.
                        if base.Type() != target.Type() {
                                break
                        }

                        if err := dw.tryToDeltify(indexMap, base, target); err != nil {
                                return err
                        }
                }
        }

        return nil
}

func (dw *deltaSelector) tryToDeltify(indexMap map[plumbing.Hash]*deltaIndex, base, target *ObjectToPack) error {
        // Original object might not be present if we're reusing a delta, so we
        // ensure it is restored.
        if err := dw.restoreOriginal(target); err != nil {
                return err
        }

        if err := dw.restoreOriginal(base); err != nil {
                return err
        }

        // If the sizes are radically different, this is a bad pairing.
        if target.Size() < base.Size()>>4 {
                return nil
        }

        msz := dw.deltaSizeLimit(
                target.Object.Size(),
                base.Depth,
                target.Depth,
                target.IsDelta(),
        )

        // Nearly impossible to fit useful delta.
        if msz <= 8 {
                return nil
        }

        // If we have to insert a lot to make this work, find another.
        if base.Size()-target.Size() > msz {
                return nil
        }

        if _, ok := indexMap[base.Hash()]; !ok {
                indexMap[base.Hash()] = new(deltaIndex)
        }

        // Now we can generate the delta using originals
        delta, err := getDelta(indexMap[base.Hash()], base.Original, target.Original)
        if err != nil {
                return err
        }

        // if delta better than target
        if delta.Size() < msz {
                target.SetDelta(base, delta)
        }

        return nil
}

func (dw *deltaSelector) deltaSizeLimit(targetSize int64, baseDepth int,
        targetDepth int, targetDelta bool) int64 {
        if !targetDelta {
                // Any delta should be no more than 50% of the original size
                // (for text files deflate of whole form should shrink 50%).
                n := targetSize >> 1

                // Evenly distribute delta size limits over allowed depth.
                // If src is non-delta (depth = 0), delta <= 50% of original.
                // If src is almost at limit (9/10), delta <= 10% of original.
                return n * (maxDepth - int64(baseDepth)) / maxDepth
        }

        // With a delta base chosen any new delta must be "better".
        // Retain the distribution described above.
        d := int64(targetDepth)
        n := targetSize

        // If target depth is bigger than maxDepth, this delta is not suitable to be used.
        if d >= maxDepth {
                return 0
        }

        // If src is whole (depth=0) and base is near limit (depth=9/10)
        // any delta using src can be 10x larger and still be better.
        //
        // If src is near limit (depth=9/10) and base is whole (depth=0)
        // a new delta dependent on src must be 1/10th the size.
        return n * (maxDepth - int64(baseDepth)) / (maxDepth - d)
}

type byTypeAndSize []*ObjectToPack

func (a byTypeAndSize) Len() int { return len(a) }

func (a byTypeAndSize) Swap(i, j int) { a[i], a[j] = a[j], a[i] }

func (a byTypeAndSize) Less(i, j int) bool {
        if a[i].Type() < a[j].Type() {
                return false
        }

        if a[i].Type() > a[j].Type() {
                return true
        }

        return a[i].Size() > a[j].Size()
}

package packfile

import (
        "bytes"

        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/utils/ioutil"
        "github.com/go-git/go-git/v6/utils/sync"
)

// See https://github.com/jelmer/dulwich/blob/master/dulwich/pack.py and
// https://github.com/tarruda/node-git-core/blob/master/src/js/delta.js
// for more info

const (
        // Standard chunk size used to generate fingerprints
        s = 16

        // https://github.com/git/git/blob/f7466e94375b3be27f229c78873f0acf8301c0a5/diff-delta.c#L428
        // Max size of a copy operation (64KB).
        maxCopySize = 64 * 1024

        // Min size of a copy operation.
        minCopySize = 4
)

// GetDelta returns an EncodedObject of type OFSDeltaObject. Base and Target object,
// will be loaded into memory to be able to create the delta object.
// To generate target again, you will need the obtained object and "base" one.
// Error will be returned if base or target object cannot be read.
func GetDelta(base, target plumbing.EncodedObject) (plumbing.EncodedObject, error) {
        return getDelta(new(deltaIndex), base, target)
}

func getDelta(index *deltaIndex, base, target plumbing.EncodedObject) (o plumbing.EncodedObject, err error) {
        br, err := base.Reader()
        if err != nil {
                return nil, err
        }

        defer ioutil.CheckClose(br, &err)

        tr, err := target.Reader()
        if err != nil {
                return nil, err
        }

        defer ioutil.CheckClose(tr, &err)

        bb := sync.GetBytesBuffer()
        defer sync.PutBytesBuffer(bb)

        _, err = bb.ReadFrom(br)
        if err != nil {
                return nil, err
        }

        tb := sync.GetBytesBuffer()
        defer sync.PutBytesBuffer(tb)

        _, err = tb.ReadFrom(tr)
        if err != nil {
                return nil, err
        }

        db := diffDelta(index, bb.Bytes(), tb.Bytes())
        delta := &plumbing.MemoryObject{}
        _, err = delta.Write(db)
        if err != nil {
                return nil, err
        }

        delta.SetSize(int64(len(db)))
        delta.SetType(plumbing.OFSDeltaObject)

        return delta, nil
}

// DiffDelta returns the delta that transforms src into tgt.
func DiffDelta(src, tgt []byte) []byte {
        return diffDelta(new(deltaIndex), src, tgt)
}

func diffDelta(index *deltaIndex, src []byte, tgt []byte) []byte {
        buf := sync.GetBytesBuffer()
        defer sync.PutBytesBuffer(buf)
        buf.Write(deltaEncodeSize(len(src)))
        buf.Write(deltaEncodeSize(len(tgt)))

        if len(index.entries) == 0 {
                index.init(src)
        }

        ibuf := sync.GetBytesBuffer()
        defer sync.PutBytesBuffer(ibuf)
        for i := 0; i < len(tgt); i++ {
                offset, l := index.findMatch(src, tgt, i)

                if l == 0 {
                        // couldn't find a match, just write the current byte and continue
                        ibuf.WriteByte(tgt[i])
                } else if l < 0 {
                        // src is less than blksz, copy the rest of the target to avoid
                        // calls to findMatch
                        for ; i < len(tgt); i++ {
                                ibuf.WriteByte(tgt[i])
                        }
                } else if l < s {
                        // remaining target is less than blksz, copy what's left of it
                        // and avoid calls to findMatch
                        for j := i; j < i+l; j++ {
                                ibuf.WriteByte(tgt[j])
                        }
                        i += l - 1
                } else {
                        encodeInsertOperation(ibuf, buf)

                        rl := l
                        aOffset := offset
                        for rl > 0 {
                                if rl < maxCopySize {
                                        buf.Write(encodeCopyOperation(aOffset, rl))
                                        break
                                }

                                buf.Write(encodeCopyOperation(aOffset, maxCopySize))
                                rl -= maxCopySize
                                aOffset += maxCopySize
                        }

                        i += l - 1
                }
        }

        encodeInsertOperation(ibuf, buf)

        // buf.Bytes() is only valid until the next modifying operation on the buffer. Copy it.
        return append([]byte{}, buf.Bytes()...)
}

func encodeInsertOperation(ibuf, buf *bytes.Buffer) {
        if ibuf.Len() == 0 {
                return
        }

        b := ibuf.Bytes()
        s := ibuf.Len()
        o := 0
        for {
                if s <= 127 {
                        break
                }
                buf.WriteByte(byte(127))
                buf.Write(b[o : o+127])
                s -= 127
                o += 127
        }
        buf.WriteByte(byte(s))
        buf.Write(b[o : o+s])

        ibuf.Reset()
}

func deltaEncodeSize(size int) []byte {
        var ret []byte
        c := size & 0x7f
        size >>= 7
        for {
                if size == 0 {
                        break
                }

                ret = append(ret, byte(c|0x80))
                c = size & 0x7f
                size >>= 7
        }
        ret = append(ret, byte(c))

        return ret
}

func encodeCopyOperation(offset, length int) []byte {
        code := 0x80
        var opcodes []byte

        var i uint
        for i = 0; i < 4; i++ {
                f := 0xff << (i * 8)
                if offset&f != 0 {
                        opcodes = append(opcodes, byte(offset&f>>(i*8)))
                        code |= 0x01 << i
                }
        }

        for i = 0; i < 3; i++ {
                f := 0xff << (i * 8)
                if length&f != 0 {
                        opcodes = append(opcodes, byte(length&f>>(i*8)))
                        code |= 0x10 << i
                }
        }

        return append([]byte{byte(code)}, opcodes...)
}

package packfile

import (
        "compress/zlib"
        "crypto"
        "fmt"
        "io"

        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/hash"
        "github.com/go-git/go-git/v6/plumbing/storer"
        "github.com/go-git/go-git/v6/utils/binary"
        "github.com/go-git/go-git/v6/utils/ioutil"
)

// Encoder gets the data from the storage and write it into the writer in PACK
// format
type Encoder struct {
        selector *deltaSelector
        w        *offsetWriter
        zw       *zlib.Writer
        hasher   plumbing.Hasher

        useRefDeltas bool
}

// NewEncoder creates a new packfile encoder using a specific Writer and
// EncodedObjectStorer. By default deltas used to generate the packfile will be
// OFSDeltaObject. To use Reference deltas, set useRefDeltas to true.
func NewEncoder(w io.Writer, s storer.EncodedObjectStorer, useRefDeltas bool) *Encoder {
        h := plumbing.Hasher{
                // TODO: Support passing an ObjectFormat (sha256)
                Hash: hash.New(crypto.SHA1),
        }
        mw := io.MultiWriter(w, h)
        ow := newOffsetWriter(mw)
        zw := zlib.NewWriter(mw)
        return &Encoder{
                selector:     newDeltaSelector(s),
                w:            ow,
                zw:           zw,
                hasher:       h,
                useRefDeltas: useRefDeltas,
        }
}

// Encode creates a packfile containing all the objects referenced in
// hashes and writes it to the writer in the Encoder.  `packWindow`
// specifies the size of the sliding window used to compare objects
// for delta compression; 0 turns off delta compression entirely.
func (e *Encoder) Encode(
        hashes []plumbing.Hash,
        packWindow uint,
) (plumbing.Hash, error) {
        objects, err := e.selector.ObjectsToPack(hashes, packWindow)
        if err != nil {
                return plumbing.ZeroHash, err
        }

        return e.encode(objects)
}

func (e *Encoder) encode(objects []*ObjectToPack) (plumbing.Hash, error) {
        if err := e.head(len(objects)); err != nil {
                return plumbing.ZeroHash, err
        }

        for _, o := range objects {
                if err := e.entry(o); err != nil {
                        return plumbing.ZeroHash, err
                }
        }

        return e.footer()
}

func (e *Encoder) head(numEntries int) error {
        return binary.Write(
                e.w,
                signature,
                int32(VersionSupported),
                int32(numEntries),
        )
}

func (e *Encoder) entry(o *ObjectToPack) (err error) {
        if o.WantWrite() {
                // A cycle exists in this delta chain. This should only occur if a
                // selected object representation disappeared during writing
                // (for example due to a concurrent repack) and a different base
                // was chosen, forcing a cycle. Select something other than a
                // delta, and write this object.
                e.selector.restoreOriginal(o)
                o.BackToOriginal()
        }

        if o.IsWritten() {
                return nil
        }

        o.MarkWantWrite()

        if err := e.writeBaseIfDelta(o); err != nil {
                return err
        }

        // We need to check if we already write that object due a cyclic delta chain
        if o.IsWritten() {
                return nil
        }

        o.Offset = e.w.Offset()

        if o.IsDelta() {
                if err := e.writeDeltaHeader(o); err != nil {
                        return err
                }
        } else {
                if err := e.entryHead(o.Type(), o.Size()); err != nil {
                        return err
                }
        }

        e.zw.Reset(e.w)

        defer ioutil.CheckClose(e.zw, &err)

        or, err := o.Object.Reader()
        if err != nil {
                return err
        }

        defer ioutil.CheckClose(or, &err)

        _, err = io.Copy(e.zw, or)
        return err
}

func (e *Encoder) writeBaseIfDelta(o *ObjectToPack) error {
        if o.IsDelta() && !o.Base.IsWritten() {
                // We must write base first
                return e.entry(o.Base)
        }

        return nil
}

func (e *Encoder) writeDeltaHeader(o *ObjectToPack) error {
        // Write offset deltas by default
        t := plumbing.OFSDeltaObject
        if e.useRefDeltas {
                t = plumbing.REFDeltaObject
        }

        if err := e.entryHead(t, o.Object.Size()); err != nil {
                return err
        }

        if e.useRefDeltas {
                return e.writeRefDeltaHeader(o.Base.Hash())
        } else {
                return e.writeOfsDeltaHeader(o)
        }
}

func (e *Encoder) writeRefDeltaHeader(base plumbing.Hash) error {
        _, err := base.WriteTo(e.w)
        return err
}

func (e *Encoder) writeOfsDeltaHeader(o *ObjectToPack) error {
        // for OFS_DELTA, offset of the base is interpreted as negative offset
        // relative to the type-byte of the header of the ofs-delta entry.
        relativeOffset := o.Offset - o.Base.Offset
        if relativeOffset <= 0 {
                return fmt.Errorf("bad offset for OFS_DELTA entry: %d", relativeOffset)
        }

        return binary.WriteVariableWidthInt(e.w, relativeOffset)
}

func (e *Encoder) entryHead(typeNum plumbing.ObjectType, size int64) error {
        t := int64(typeNum)
        header := []byte{}
        c := (t << firstLengthBits) | (size & maskFirstLength)
        size >>= firstLengthBits
        for {
                if size == 0 {
                        break
                }
                header = append(header, byte(c|maskContinue))
                c = size & int64(maskLength)
                size >>= lengthBits
        }

        header = append(header, byte(c))
        _, err := e.w.Write(header)

        return err
}

func (e *Encoder) footer() (plumbing.Hash, error) {
        h := e.hasher.Sum()
        _, err := h.WriteTo(e.w)
        return h, err
}

type offsetWriter struct {
        w      io.Writer
        offset int64
}

func newOffsetWriter(w io.Writer) *offsetWriter {
        return &offsetWriter{w: w}
}

func (ow *offsetWriter) Write(p []byte) (n int, err error) {
        n, err = ow.w.Write(p)
        ow.offset += int64(n)
        return n, err
}

func (ow *offsetWriter) Offset() int64 {
        return ow.offset
}

package packfile

import "fmt"

// Error specifies errors returned during packfile parsing.
type Error struct {
        reason, details string
}

// NewError returns a new error.
func NewError(reason string) *Error {
        return &Error{reason: reason}
}

// Error returns a text representation of the error.
func (e *Error) Error() string {
        if e.details == "" {
                return e.reason
        }

        return fmt.Sprintf("%s: %s", e.reason, e.details)
}

// AddDetails adds details to an error, with additional text.
func (e *Error) AddDetails(format string, args ...interface{}) *Error {
        return &Error{
                reason:  e.reason,
                details: fmt.Sprintf(format, args...),
        }
}

package packfile

import (
        "errors"
        "io"
        "os"

        billy "github.com/go-git/go-billy/v5"
        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/cache"
        "github.com/go-git/go-git/v6/plumbing/format/idxfile"
        "github.com/go-git/go-git/v6/utils/sync"
)

// FSObject is an object from the packfile on the filesystem.
type FSObject struct {
        hash     plumbing.Hash
        offset   int64
        size     int64
        typ      plumbing.ObjectType
        index    idxfile.Index
        fs       billy.Filesystem
        pack     billy.File
        packPath string
        cache    cache.Object
}

// NewFSObject creates a new filesystem object.
func NewFSObject(
        hash plumbing.Hash,
        finalType plumbing.ObjectType,
        offset int64,
        contentSize int64,
        index idxfile.Index,
        fs billy.Filesystem,
        pack billy.File,
        packPath string,
        cache cache.Object,
) *FSObject {
        return &FSObject{
                hash:     hash,
                offset:   offset,
                size:     contentSize,
                typ:      finalType,
                index:    index,
                fs:       fs,
                pack:     pack,
                packPath: packPath,
                cache:    cache,
        }
}

// Reader implements the plumbing.EncodedObject interface.
func (o *FSObject) Reader() (io.ReadCloser, error) {
        obj, ok := o.cache.Get(o.hash)
        if ok && obj != o {
                reader, err := obj.Reader()
                if err != nil {
                        return nil, err
                }

                return reader, nil
        }

        var closer io.Closer
        _, err := o.pack.Seek(o.offset, io.SeekStart)
        // fsobject aims to reuse an existing file descriptor to the packfile.
        // In some cases that descriptor would already be closed, in such cases,
        // open the packfile again and close it when the reader is closed.
        if err != nil && errors.Is(err, os.ErrClosed) {
                o.pack, err = o.fs.Open(o.packPath)
                if err != nil {
                        return nil, err
                }
                closer = o.pack
                _, err = o.pack.Seek(o.offset, io.SeekStart)
        }
        if err != nil {
                return nil, err
        }

        dict := sync.GetByteSlice()
        zr := sync.NewZlibReader(dict)
        err = zr.Reset(o.pack)
        if err != nil {
                return nil, err
        }
        return &zlibReadCloser{zr, dict, closer}, nil
}

type zlibReadCloser struct {
        r    sync.ZLibReader
        dict *[]byte
        f    io.Closer
}

// Read reads up to len(p) bytes into p from the data.
func (r *zlibReadCloser) Read(p []byte) (int, error) {
        return r.r.Reader.Read(p)
}

func (r *zlibReadCloser) Close() error {
        sync.PutByteSlice(r.dict)
        sync.PutZlibReader(r.r)
        if r.f != nil {
                r.f.Close()
        }
        return nil
}

// SetSize implements the plumbing.EncodedObject interface. This method
// is a noop.
func (o *FSObject) SetSize(int64) {}

// SetType implements the plumbing.EncodedObject interface. This method is
// a noop.
func (o *FSObject) SetType(plumbing.ObjectType) {}

// Hash implements the plumbing.EncodedObject interface.
func (o *FSObject) Hash() plumbing.Hash { return o.hash }

// Size implements the plumbing.EncodedObject interface.
func (o *FSObject) Size() int64 { return o.size }

// Type implements the plumbing.EncodedObject interface.
func (o *FSObject) Type() plumbing.ObjectType {
        return o.typ
}

// Writer implements the plumbing.EncodedObject interface. This method always
// returns a nil writer.
func (o *FSObject) Writer() (io.WriteCloser, error) {
        return nil, nil
}

package packfile

import (
        "github.com/go-git/go-git/v6/plumbing"
)

// ObjectToPack is a representation of an object that is going to be into a
// pack file.
type ObjectToPack struct {
        // The main object to pack, it could be any object, including deltas.
        Object plumbing.EncodedObject
        // Base is the object that a delta is based on, which could also be another delta.
        // Nil when the main object is not a delta.
        Base *ObjectToPack
        // Original is the object that we can generate applying the delta to
        // Base, or the same object as Object in the case of a non-delta
        // object.
        Original plumbing.EncodedObject
        // Depth is the amount of deltas needed to resolve to obtain Original
        // (delta based on delta based on ...)
        Depth int

        // offset in pack when object has been already written, or 0 if it
        // has not been written yet
        Offset int64

        // Information from the original object
        resolvedOriginal bool
        originalType     plumbing.ObjectType
        originalSize     int64
        originalHash     plumbing.Hash
}

// newObjectToPack creates a correct ObjectToPack based on a non-delta object
func newObjectToPack(o plumbing.EncodedObject) *ObjectToPack {
        return &ObjectToPack{
                Object:   o,
                Original: o,
        }
}

// newDeltaObjectToPack creates a correct ObjectToPack for a delta object, based on
// his base (could be another delta), the delta target (in this case called original),
// and the delta Object itself
func newDeltaObjectToPack(base *ObjectToPack, original, delta plumbing.EncodedObject) *ObjectToPack {
        return &ObjectToPack{
                Object:   delta,
                Base:     base,
                Original: original,
                Depth:    base.Depth + 1,
        }
}

// BackToOriginal converts that ObjectToPack to a non-deltified object if it was one
func (o *ObjectToPack) BackToOriginal() {
        if o.IsDelta() && o.Original != nil {
                o.Object = o.Original
                o.Base = nil
                o.Depth = 0
        }
}

// IsWritten returns if that ObjectToPack was
// already written into the packfile or not
func (o *ObjectToPack) IsWritten() bool {
        return o.Offset > 1
}

// MarkWantWrite marks this ObjectToPack as WantWrite
// to avoid delta chain loops
func (o *ObjectToPack) MarkWantWrite() {
        o.Offset = 1
}

// WantWrite checks if this ObjectToPack was marked as WantWrite before
func (o *ObjectToPack) WantWrite() bool {
        return o.Offset == 1
}

// SetOriginal sets both Original and saves size, type and hash. If object
// is nil Original is set but previous resolved values are kept
func (o *ObjectToPack) SetOriginal(obj plumbing.EncodedObject) {
        o.Original = obj
        o.SaveOriginalMetadata()
}

// SaveOriginalMetadata saves size, type and hash of Original object
func (o *ObjectToPack) SaveOriginalMetadata() {
        if o.Original != nil {
                o.originalSize = o.Original.Size()
                o.originalType = o.Original.Type()
                o.originalHash = o.Original.Hash()
                o.resolvedOriginal = true
        }
}

// CleanOriginal sets Original to nil
func (o *ObjectToPack) CleanOriginal() {
        o.Original = nil
}

func (o *ObjectToPack) Type() plumbing.ObjectType {
        if o.Original != nil {
                return o.Original.Type()
        }

        if o.resolvedOriginal {
                return o.originalType
        }

        if o.Base != nil {
                return o.Base.Type()
        }

        if o.Object != nil {
                return o.Object.Type()
        }

        panic("cannot get type")
}

func (o *ObjectToPack) Hash() plumbing.Hash {
        if o.Original != nil {
                return o.Original.Hash()
        }

        if o.resolvedOriginal {
                return o.originalHash
        }

        do, ok := o.Object.(plumbing.DeltaObject)
        if ok {
                return do.ActualHash()
        }

        panic("cannot get hash")
}

func (o *ObjectToPack) Size() int64 {
        if o.Original != nil {
                return o.Original.Size()
        }

        if o.resolvedOriginal {
                return o.originalSize
        }

        do, ok := o.Object.(plumbing.DeltaObject)
        if ok {
                return do.ActualSize()
        }

        panic("cannot get ObjectToPack size")
}

func (o *ObjectToPack) IsDelta() bool {
        return o.Base != nil
}

func (o *ObjectToPack) SetDelta(base *ObjectToPack, delta plumbing.EncodedObject) {
        o.Object = delta
        o.Base = base
        o.Depth = base.Depth + 1
}

package packfile

import (
        "crypto"
        "fmt"
        "io"
        "os"
        "sync"

        billy "github.com/go-git/go-billy/v5"
        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/cache"
        format "github.com/go-git/go-git/v6/plumbing/format/config"
        "github.com/go-git/go-git/v6/plumbing/format/idxfile"
        "github.com/go-git/go-git/v6/plumbing/storer"
        "github.com/go-git/go-git/v6/utils/ioutil"
)

var (
        // ErrInvalidObject is returned by Decode when an invalid object is
        // found in the packfile.
        ErrInvalidObject = NewError("invalid git object")
        // ErrZLib is returned by Decode when there was an error unzipping
        // the packfile contents.
        ErrZLib = NewError("zlib reading error")
)

// Packfile allows retrieving information from inside a packfile.
type Packfile struct {
        idxfile.Index
        fs      billy.Filesystem
        file    billy.File
        scanner *Scanner

        cache cache.Object

        id           plumbing.Hash
        m            sync.Mutex
        objectIdSize int

        once    sync.Once
        onceErr error
}

// NewPackfile returns a packfile representation for the given packfile file
// and packfile idx.
// If the filesystem is provided, the packfile will return FSObjects, otherwise
// it will return MemoryObjects.
func NewPackfile(
        file billy.File,
        opts ...PackfileOption,
) *Packfile {
        p := &Packfile{
                file:         file,
                objectIdSize: crypto.SHA1.Size(),
        }
        for _, opt := range opts {
                opt(p)
        }

        return p
}

// Get retrieves the encoded object in the packfile with the given hash.
func (p *Packfile) Get(h plumbing.Hash) (plumbing.EncodedObject, error) {
        if err := p.init(); err != nil {
                return nil, err
        }
        p.m.Lock()
        defer p.m.Unlock()

        return p.get(h)
}

// GetByOffset retrieves the encoded object from the packfile at the given
// offset.
func (p *Packfile) GetByOffset(offset int64) (plumbing.EncodedObject, error) {
        if err := p.init(); err != nil {
                return nil, err
        }
        p.m.Lock()
        defer p.m.Unlock()

        return p.getByOffset(offset)
}

// GetSizeByOffset retrieves the size of the encoded object from the
// packfile with the given offset.
func (p *Packfile) GetSizeByOffset(offset int64) (size int64, err error) {
        if err := p.init(); err != nil {
                return 0, err
        }

        d, err := p.GetByOffset(offset)
        if err != nil {
                return 0, err
        }

        return d.Size(), nil
}

// GetAll returns an iterator with all encoded objects in the packfile.
// The iterator returned is not thread-safe, it should be used in the same
// thread as the Packfile instance.
func (p *Packfile) GetAll() (storer.EncodedObjectIter, error) {
        return p.GetByType(plumbing.AnyObject)
}

// GetByType returns all the objects of the given type.
func (p *Packfile) GetByType(typ plumbing.ObjectType) (storer.EncodedObjectIter, error) {
        if err := p.init(); err != nil {
                return nil, err
        }

        switch typ {
        case plumbing.AnyObject,
                plumbing.BlobObject,
                plumbing.TreeObject,
                plumbing.CommitObject,
                plumbing.TagObject:
                entries, err := p.EntriesByOffset()
                if err != nil {
                        return nil, err
                }

                return &objectIter{
                        p:    p,
                        iter: entries,
                        typ:  typ,
                }, nil
        default:
                return nil, plumbing.ErrInvalidType
        }
}

// Returns the Packfile's inner scanner.
//
// Deprecated: this will be removed in future versions of the packfile package
// to avoid exposing the package internals and to improve its thread-safety.
// TODO: Remove Scanner method
func (p *Packfile) Scanner() (*Scanner, error) {
        if err := p.init(); err != nil {
                return nil, err
        }

        return p.scanner, nil
}

// ID returns the ID of the packfile, which is the checksum at the end of it.
func (p *Packfile) ID() (plumbing.Hash, error) {
        if err := p.init(); err != nil {
                return plumbing.ZeroHash, err
        }

        return p.id, nil
}

// get is not threat-safe, and should only be called within packfile.go.
func (p *Packfile) get(h plumbing.Hash) (plumbing.EncodedObject, error) {
        if obj, ok := p.cache.Get(h); ok {
                return obj, nil
        }

        offset, err := p.Index.FindOffset(h)
        if err != nil {
                return nil, err
        }

        oh, err := p.headerFromOffset(offset)
        if err != nil {
                return nil, err
        }

        return p.objectFromHeader(oh)
}

// getByOffset is not threat-safe, and should only be called within packfile.go.
func (p *Packfile) getByOffset(offset int64) (plumbing.EncodedObject, error) {
        h, err := p.FindHash(offset)
        if err != nil {
                return nil, err
        }

        if obj, ok := p.cache.Get(h); ok {
                return obj, nil
        }

        oh, err := p.headerFromOffset(offset)
        if err != nil {
                return nil, err
        }

        return p.objectFromHeader(oh)
}

func (p *Packfile) init() error {
        p.once.Do(func() {
                if p.file == nil {
                        p.onceErr = fmt.Errorf("file is not set")
                        return
                }

                if p.Index == nil {
                        p.onceErr = fmt.Errorf("index is not set")
                        return
                }

                var opts []ScannerOption
                if p.objectIdSize == format.SHA256Size {
                        opts = append(opts, WithSHA256())
                }

                p.scanner = NewScanner(p.file, opts...)
                // Validate packfile signature.
                if !p.scanner.Scan() {
                        p.onceErr = p.scanner.Error()
                        return
                }

                _, err := p.scanner.Seek(-int64(p.objectIdSize), io.SeekEnd)
                if err != nil {
                        p.onceErr = err
                        return
                }

                p.id.ResetBySize(p.objectIdSize)
                _, err = p.id.ReadFrom(p.scanner)
                if err != nil {
                        p.onceErr = err
                }

                if p.cache == nil {
                        p.cache = cache.NewObjectLRUDefault()
                }
        })

        return p.onceErr
}

func (p *Packfile) headerFromOffset(offset int64) (*ObjectHeader, error) {
        err := p.scanner.SeekFromStart(offset)
        if err != nil {
                return nil, err
        }

        if !p.scanner.Scan() {
                return nil, plumbing.ErrObjectNotFound
        }

        oh := p.scanner.Data().Value().(ObjectHeader)
        return &oh, nil
}

// Close the packfile and its resources.
func (p *Packfile) Close() error {
        p.m.Lock()
        defer p.m.Unlock()

        closer, ok := p.file.(io.Closer)
        if !ok {
                return nil
        }

        return closer.Close()
}

func (p *Packfile) objectFromHeader(oh *ObjectHeader) (plumbing.EncodedObject, error) {
        if oh == nil {
                return nil, plumbing.ErrObjectNotFound
        }

        // If we have filesystem, and the object is not a delta type, return a FSObject.
        // This avoids having to inflate the object more than once.
        if !oh.Type.IsDelta() && p.fs != nil {
                fs := NewFSObject(
                        oh.ID(),
                        oh.Type,
                        oh.ContentOffset,
                        oh.Size,
                        p.Index,
                        p.fs,
                        p.file,
                        p.file.Name(),
                        p.cache,
                )

                p.cache.Put(fs)
                return fs, nil
        }

        return p.getMemoryObject(oh)
}

func (p *Packfile) getMemoryObject(oh *ObjectHeader) (plumbing.EncodedObject, error) {
        var obj = new(plumbing.MemoryObject)
        obj.SetSize(oh.Size)
        obj.SetType(oh.Type)

        w, err := obj.Writer()
        if err != nil {
                return nil, err
        }
        defer ioutil.CheckClose(w, &err)

        switch oh.Type {
        case plumbing.CommitObject, plumbing.TreeObject, plumbing.BlobObject, plumbing.TagObject:
                err = p.scanner.inflateContent(oh.ContentOffset, w)

        case plumbing.REFDeltaObject, plumbing.OFSDeltaObject:
                var parent plumbing.EncodedObject

                switch oh.Type {
                case plumbing.REFDeltaObject:
                        var ok bool
                        parent, ok = p.cache.Get(oh.Reference)
                        if !ok {
                                parent, err = p.get(oh.Reference)
                        }
                case plumbing.OFSDeltaObject:
                        parent, err = p.getByOffset(oh.OffsetReference)
                }

                if err != nil {
                        return nil, fmt.Errorf("cannot find base object: %w", err)
                }

                err = p.scanner.inflateContent(oh.ContentOffset, &oh.content)
                if err != nil {
                        return nil, fmt.Errorf("cannot inflate content: %w", err)
                }

                obj.SetType(parent.Type())
                err = ApplyDelta(obj, parent, oh.content.Bytes()) //nolint:ineffassign

        default:
                err = ErrInvalidObject.AddDetails("type %q", oh.Type)
        }

        if err != nil {
                return nil, err
        }

        p.cache.Put(obj)

        return obj, nil
}

// isInvalid checks whether an error is an os.PathError with an os.ErrInvalid
// error inside. It also checks for the windows error, which is different from
// os.ErrInvalid.
func isInvalid(err error) bool {
        pe, ok := err.(*os.PathError)
        if !ok {
                return false
        }

        errstr := pe.Err.Error()
        return errstr == errInvalidUnix || errstr == errInvalidWindows
}

// errInvalidWindows is the Windows equivalent to os.ErrInvalid
const errInvalidWindows = "The parameter is incorrect."

var errInvalidUnix = os.ErrInvalid.Error()

package packfile

import (
        "io"

        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/format/idxfile"
)

type objectIter struct {
        p    *Packfile
        typ  plumbing.ObjectType
        iter idxfile.EntryIter
}

func (i *objectIter) Next() (plumbing.EncodedObject, error) {
        if err := i.p.init(); err != nil {
                return nil, err
        }

        i.p.m.Lock()
        defer i.p.m.Unlock()

        return i.next()
}

func (i *objectIter) next() (plumbing.EncodedObject, error) {
        for {
                e, err := i.iter.Next()
                if err != nil {
                        return nil, err
                }

                oh, err := i.p.headerFromOffset(int64(e.Offset))
                if err != nil {
                        return nil, err
                }

                if i.typ == plumbing.AnyObject {
                        return i.p.objectFromHeader(oh)
                }

                // Current object header type is a delta, get the actual object to
                // assess the actual type.
                if oh.Type.IsDelta() {
                        o, err := i.p.objectFromHeader(oh)
                        if o.Type() == i.typ {
                                return o, err
                        }

                        continue
                }

                if oh.Type == i.typ {
                        return i.p.objectFromHeader(oh)
                }

                continue
        }
}

func (i *objectIter) ForEach(f func(plumbing.EncodedObject) error) error {
        if err := i.p.init(); err != nil {
                return err
        }

        i.p.m.Lock()
        defer i.p.m.Unlock()

        for {
                o, err := i.next()
                if err != nil {
                        if err == io.EOF {
                                return nil
                        }
                        return err
                }

                if err := f(o); err != nil {
                        return err
                }
        }
}

func (i *objectIter) Close() {
        i.p.m.Lock()
        defer i.p.m.Unlock()

        i.iter.Close()
}

package packfile

import (
        billy "github.com/go-git/go-billy/v5"
        "github.com/go-git/go-git/v6/plumbing/cache"
        "github.com/go-git/go-git/v6/plumbing/format/idxfile"
)

type PackfileOption func(*Packfile)

// WithCache sets the cache to be used throughout Packfile operations.
// Use this to share existing caches with the Packfile. If not used, a
// new cache instance will be created.
func WithCache(cache cache.Object) PackfileOption {
        return func(p *Packfile) {
                p.cache = cache
        }
}

// WithIdx sets the idxfile for the packfile.
func WithIdx(idx idxfile.Index) PackfileOption {
        return func(p *Packfile) {
                p.Index = idx
        }
}

// WithFs sets the filesystem to be used.
func WithFs(fs billy.Filesystem) PackfileOption {
        return func(p *Packfile) {
                p.fs = fs
        }
}

// WithObjectIDSize sets the size of the object IDs inside the packfile.
// Valid options are hash.SHA1Size and hash.SHA256Size.
//
// When no object ID size is set, hash.SHA1Size will be used.
func WithObjectIDSize(sz int) PackfileOption {
        return func(p *Packfile) {
                p.objectIdSize = sz
        }
}

package packfile

import (
        "bytes"
        "errors"
        "fmt"
        "io"
        stdsync "sync"

        "github.com/go-git/go-git/v6/plumbing"
        format "github.com/go-git/go-git/v6/plumbing/format/config"
        "github.com/go-git/go-git/v6/plumbing/storer"
        "github.com/go-git/go-git/v6/utils/ioutil"
)

var (
        // ErrReferenceDeltaNotFound is returned when the reference delta is not
        // found.
        ErrReferenceDeltaNotFound = errors.New("reference delta not found")

        // ErrNotSeekableSource is returned when the source for the parser is not
        // seekable and a storage was not provided, so it can't be parsed.
        ErrNotSeekableSource = errors.New("parser source is not seekable and storage was not provided")

        // ErrDeltaNotCached is returned when the delta could not be found in cache.
        ErrDeltaNotCached = errors.New("delta could not be found in cache")
)

// Parser decodes a packfile and calls any observer associated to it. Is used
// to generate indexes.
type Parser struct {
        storage storer.EncodedObjectStorer
        cache   *parserCache

        scanner   *Scanner
        observers []Observer
        hasher    plumbing.Hasher

        checksum plumbing.Hash
        m        stdsync.Mutex
}

// NewParser creates a new Parser.
// When a storage is set, the objects are written to storage as they
// are parsed.
func NewParser(data io.Reader, opts ...ParserOption) *Parser {
        p := &Parser{
                hasher: plumbing.NewHasher(format.SHA1, plumbing.AnyObject, 0),
        }
        for _, opt := range opts {
                opt(p)
        }

        p.scanner = NewScanner(data)

        if p.storage != nil {
                p.scanner.storage = p.storage
        }
        p.cache = newParserCache()

        return p
}

func (p *Parser) storeOrCache(oh *ObjectHeader) error {
        // Only need to store deltas, as the scanner already stored non-delta
        // objects.
        if p.storage != nil && oh.diskType.IsDelta() {
                w, err := p.storage.RawObjectWriter(oh.Type, oh.Size)
                if err != nil {
                        return err
                }

                defer w.Close()

                _, err = io.Copy(w, bytes.NewReader(oh.content.Bytes()))
                if err != nil {
                        return err
                }
        }

        if p.cache != nil {
                p.cache.Add(oh)
        }

        if err := p.onInflatedObjectHeader(oh.Type, oh.Size, oh.Offset); err != nil {
                return err
        }

        if err := p.onInflatedObjectContent(oh.Hash, oh.Offset, oh.Crc32, nil); err != nil {
                return err
        }

        return nil
}

func (p *Parser) resetCache(qty int) {
        if p.cache != nil {
                p.cache.Reset(qty)
        }
}

// Parse start decoding phase of the packfile.
func (p *Parser) Parse() (plumbing.Hash, error) {
        p.m.Lock()
        defer p.m.Unlock()

        var pendingDeltas []*ObjectHeader
        var pendingDeltaREFs []*ObjectHeader

        for p.scanner.Scan() {
                data := p.scanner.Data()
                switch data.Section {
                case HeaderSection:
                        header := data.Value().(Header)

                        p.resetCache(int(header.ObjectsQty))
                        p.onHeader(header.ObjectsQty)

                case ObjectSection:
                        oh := data.Value().(ObjectHeader)
                        if oh.Type.IsDelta() {
                                if oh.Type == plumbing.OFSDeltaObject {
                                        pendingDeltas = append(pendingDeltas, &oh)
                                } else if oh.Type == plumbing.REFDeltaObject {
                                        pendingDeltaREFs = append(pendingDeltaREFs, &oh)
                                }
                                continue
                        } else {
                                p.storeOrCache(&oh)
                        }

                case FooterSection:
                        p.checksum = data.Value().(plumbing.Hash)
                }
        }

        if p.scanner.objects == 0 {
                return plumbing.ZeroHash, ErrEmptyPackfile
        }

        for _, oh := range pendingDeltaREFs {
                err := p.processDelta(oh)
                if err != nil {
                        return plumbing.ZeroHash, err
                }
        }

        for _, oh := range pendingDeltas {
                err := p.processDelta(oh)
                if err != nil {
                        return plumbing.ZeroHash, err
                }
        }

        return p.checksum, p.onFooter(p.checksum)
}

func (p *Parser) processDelta(oh *ObjectHeader) error {
        switch oh.Type {
        case plumbing.OFSDeltaObject:
                pa, ok := p.cache.oiByOffset[oh.OffsetReference]
                if !ok {
                        return plumbing.ErrObjectNotFound
                }
                oh.parent = pa

        case plumbing.REFDeltaObject:
                pa, ok := p.cache.oiByHash[oh.Reference]
                if !ok {
                        // can't find referenced object in this pack file
                        // this must be a "thin" pack.
                        oh.parent = &ObjectHeader{ // Placeholder parent
                                Hash:        oh.Reference,
                                externalRef: true, // mark as an external reference that must be resolved
                                Type:        plumbing.AnyObject,
                                diskType:    plumbing.AnyObject,
                        }
                } else {
                        oh.parent = pa
                }
                p.cache.oiByHash[oh.Reference] = oh.parent

        default:
                return fmt.Errorf("unsupported delta type: %v", oh.Type)
        }

        parentContents, err := p.parentReader(oh.parent)
        if err != nil {
                return err
        }

        var deltaData bytes.Buffer
        if oh.content.Len() > 0 {
                _, err = oh.content.WriteTo(&deltaData)
                if err != nil {
                        return err
                }
        } else {
                deltaData = *bytes.NewBuffer(make([]byte, 0, oh.Size))
                err = p.scanner.inflateContent(oh.ContentOffset, &deltaData)
                if err != nil {
                        return err
                }
        }

        w, err := p.cacheWriter(oh)
        if err != nil {
                return err
        }

        defer w.Close()

        err = applyPatchBaseHeader(oh, parentContents, &deltaData, w, nil)
        if err != nil {
                return err
        }

        return p.storeOrCache(oh)
}

func (p *Parser) parentReader(parent *ObjectHeader) (io.ReaderAt, error) {
        // If parent is a Delta object, the inflated object must come
        // from either cache or storage, else we would need to inflate
        // it to then inflate the current object, which could go on
        // indefinitely.

        if p.storage != nil && parent.Hash != plumbing.ZeroHash {
                obj, err := p.storage.EncodedObject(parent.Type, parent.Hash)
                if err == nil {
                        // Ensure that external references have the correct type and size.
                        parent.Type = obj.Type()
                        parent.Size = obj.Size()
                        r, err := obj.Reader()
                        if err == nil {
                                parentData := bytes.NewBuffer(make([]byte, 0, parent.Size))

                                _, err = io.Copy(parentData, r)
                                r.Close()

                                if err == nil {
                                        return bytes.NewReader(parentData.Bytes()), nil
                                }
                        }
                }
        }

        if p.cache != nil && parent.content.Len() > 0 {
                return bytes.NewReader(parent.content.Bytes()), nil
        }

        // If the parent is not an external ref and we don't have the
        // content offset, we won't be able to inflate via seeking through
        // the packfile.
        if !parent.externalRef && parent.ContentOffset == 0 {
                return nil, plumbing.ErrObjectNotFound
        }

        // Not a seeker data source, so avoid seeking the content.
        if p.scanner.seeker == nil {
                return nil, plumbing.ErrObjectNotFound
        }

        parentData := bytes.NewBuffer(make([]byte, 0, parent.Size))
        err := p.scanner.inflateContent(parent.ContentOffset, parentData)
        if err != nil {
                return nil, ErrReferenceDeltaNotFound
        }
        return bytes.NewReader(parentData.Bytes()), nil
}

func (p *Parser) cacheWriter(oh *ObjectHeader) (io.WriteCloser, error) {
        return ioutil.NewWriteCloser(&oh.content, nil), nil
}

func applyPatchBaseHeader(ota *ObjectHeader, base io.ReaderAt, delta io.Reader, target io.Writer, wh objectHeaderWriter) error {
        if target == nil {
                return fmt.Errorf("cannot apply patch against nil target")
        }

        typ := ota.Type
        if ota.Hash == plumbing.ZeroHash {
                typ = ota.parent.Type
        }

        sz, h, err := patchDeltaWriter(target, base, delta, typ, wh)
        if err != nil {
                return err
        }

        if ota.Hash == plumbing.ZeroHash {
                ota.Type = typ
                ota.Size = int64(sz)
                ota.Hash = h
        }

        return nil
}

func (p *Parser) forEachObserver(f func(o Observer) error) error {
        for _, o := range p.observers {
                if err := f(o); err != nil {
                        return err
                }
        }
        return nil
}

func (p *Parser) onHeader(count uint32) error {
        return p.forEachObserver(func(o Observer) error {
                return o.OnHeader(count)
        })
}

func (p *Parser) onInflatedObjectHeader(
        t plumbing.ObjectType,
        objSize int64,
        pos int64,
) error {
        return p.forEachObserver(func(o Observer) error {
                return o.OnInflatedObjectHeader(t, objSize, pos)
        })
}

func (p *Parser) onInflatedObjectContent(
        h plumbing.Hash,
        pos int64,
        crc uint32,
        content []byte,
) error {
        return p.forEachObserver(func(o Observer) error {
                return o.OnInflatedObjectContent(h, pos, crc, content)
        })
}

func (p *Parser) onFooter(h plumbing.Hash) error {
        return p.forEachObserver(func(o Observer) error {
                return o.OnFooter(h)
        })
}

package packfile

import (
        "slices"

        "github.com/go-git/go-git/v6/plumbing"
        "golang.org/x/exp/maps"
)

func newParserCache() *parserCache {
        c := &parserCache{}
        return c
}

// parserCache defines the cache used within the parser.
// This is not thread safe by itself, and relies on the parser to
// enforce thread-safety.
type parserCache struct {
        oi         []*ObjectHeader
        oiByHash   map[plumbing.Hash]*ObjectHeader
        oiByOffset map[int64]*ObjectHeader
}

func (c *parserCache) Add(oh *ObjectHeader) {
        c.oiByHash[oh.Hash] = oh
        c.oiByOffset[oh.Offset] = oh
        c.oi = append(c.oi, oh)
}

func (c *parserCache) Reset(n int) {
        if c.oi == nil {
                c.oi = make([]*ObjectHeader, 0, n)
                c.oiByHash = make(map[plumbing.Hash]*ObjectHeader, n)
                c.oiByOffset = make(map[int64]*ObjectHeader, n)
        } else {
                c.oi = c.oi[:0]
                c.oi = slices.Grow(c.oi, n)

                maps.Clear(c.oiByHash)
                maps.Clear(c.oiByOffset)
        }
}

package packfile

import (
        "github.com/go-git/go-git/v6/plumbing/storer"
)

type ParserOption func(*Parser)

// WithStorage sets the storage to be used while parsing a pack file.
func WithStorage(storage storer.EncodedObjectStorer) ParserOption {
        return func(p *Parser) {
                p.storage = storage
        }
}

// WithScannerObservers sets the observers to be notified during the
// scanning or parsing of a pack file. The scanner is responsible for
// notifying observers around general pack file information, such as
// header and footer. The scanner also notifies object headers for
// non-delta objects.
//
// Delta objects are notified as part of the parser logic.
func WithScannerObservers(ob ...Observer) ParserOption {
        return func(p *Parser) {
                p.observers = ob
        }
}

package packfile

import (
        "bufio"
        "bytes"
        "errors"
        "fmt"
        "io"
        "math"

        "github.com/go-git/go-git/v6/plumbing"
        format "github.com/go-git/go-git/v6/plumbing/format/config"
        "github.com/go-git/go-git/v6/utils/ioutil"
        "github.com/go-git/go-git/v6/utils/sync"
)

// See https://github.com/git/git/blob/49fa3dc76179e04b0833542fa52d0f287a4955ac/delta.h
// https://github.com/git/git/blob/c2c5f6b1e479f2c38e0e01345350620944e3527f/patch-delta.c,
// and https://github.com/tarruda/node-git-core/blob/master/src/js/delta.js
// for details about the delta format.

var (
        ErrInvalidDelta = errors.New("invalid delta")
        ErrDeltaCmd     = errors.New("wrong delta command")
)

const (
        payload      = 0x7f // 0111 1111
        continuation = 0x80 // 1000 0000

        // maxPatchPreemptionSize defines what is the max size of bytes to be
        // premptively made available for a patch operation.
        maxPatchPreemptionSize uint = 65536

        // minDeltaSize defines the smallest size for a delta.
        minDeltaSize = 4
)

type offset struct {
        mask  byte
        shift uint
}

var offsets = []offset{
        {mask: 0x01, shift: 0},
        {mask: 0x02, shift: 8},
        {mask: 0x04, shift: 16},
        {mask: 0x08, shift: 24},
}

var sizes = []offset{
        {mask: 0x10, shift: 0},
        {mask: 0x20, shift: 8},
        {mask: 0x40, shift: 16},
}

// ApplyDelta writes to target the result of applying the modification deltas in delta to base.
func ApplyDelta(target, base plumbing.EncodedObject, delta []byte) (err error) {
        r, err := base.Reader()
        if err != nil {
                return err
        }

        defer ioutil.CheckClose(r, &err)

        w, err := target.Writer()
        if err != nil {
                return err
        }

        defer ioutil.CheckClose(w, &err)

        buf := sync.GetBytesBuffer()
        defer sync.PutBytesBuffer(buf)
        _, err = buf.ReadFrom(r)
        if err != nil {
                return err
        }
        src := buf.Bytes()

        dst := sync.GetBytesBuffer()
        defer sync.PutBytesBuffer(dst)
        err = patchDelta(dst, src, delta)
        if err != nil {
                return err
        }

        target.SetSize(int64(dst.Len()))

        b := sync.GetByteSlice()
        _, err = io.CopyBuffer(w, dst, *b)
        sync.PutByteSlice(b)
        return err
}

// PatchDelta returns the result of applying the modification deltas in delta to src.
// An error will be returned if delta is corrupted (ErrInvalidDelta) or an action command
// is not copy from source or copy from delta (ErrDeltaCmd).
func PatchDelta(src, delta []byte) ([]byte, error) {
        if len(src) == 0 || len(delta) < minDeltaSize {
                return nil, ErrInvalidDelta
        }

        b := &bytes.Buffer{}
        if err := patchDelta(b, src, delta); err != nil {
                return nil, err
        }
        return b.Bytes(), nil
}

func ReaderFromDelta(base plumbing.EncodedObject, deltaRC io.Reader) (io.ReadCloser, error) {
        deltaBuf := bufio.NewReaderSize(deltaRC, 1024)
        srcSz, err := decodeLEB128ByteReader(deltaBuf)
        if err != nil {
                if err == io.EOF {
                        return nil, ErrInvalidDelta
                }
                return nil, err
        }
        if srcSz != uint(base.Size()) {
                return nil, ErrInvalidDelta
        }

        targetSz, err := decodeLEB128ByteReader(deltaBuf)
        if err != nil {
                if err == io.EOF {
                        return nil, ErrInvalidDelta
                }
                return nil, err
        }
        remainingTargetSz := targetSz

        dstRd, dstWr := io.Pipe()

        go func() {
                baseRd, err := base.Reader()
                if err != nil {
                        _ = dstWr.CloseWithError(ErrInvalidDelta)
                        return
                }
                defer baseRd.Close()

                baseBuf := bufio.NewReader(baseRd)
                basePos := uint(0)

                for {
                        cmd, err := deltaBuf.ReadByte()
                        if err == io.EOF {
                                _ = dstWr.CloseWithError(ErrInvalidDelta)
                                return
                        }
                        if err != nil {
                                _ = dstWr.CloseWithError(err)
                                return
                        }

                        switch {
                        case isCopyFromSrc(cmd):
                                offset, err := decodeOffsetByteReader(cmd, deltaBuf)
                                if err != nil {
                                        _ = dstWr.CloseWithError(err)
                                        return
                                }
                                sz, err := decodeSizeByteReader(cmd, deltaBuf)
                                if err != nil {
                                        _ = dstWr.CloseWithError(err)
                                        return
                                }

                                if invalidSize(sz, targetSz) ||
                                        invalidOffsetSize(offset, sz, srcSz) {
                                        _ = dstWr.Close()
                                        return
                                }

                                discard := offset - basePos
                                if basePos > offset {
                                        _ = baseRd.Close()
                                        baseRd, err = base.Reader()
                                        if err != nil {
                                                _ = dstWr.CloseWithError(ErrInvalidDelta)
                                                return
                                        }
                                        baseBuf.Reset(baseRd)
                                        discard = offset
                                }
                                for discard > math.MaxInt32 {
                                        n, err := baseBuf.Discard(math.MaxInt32)
                                        if err != nil {
                                                _ = dstWr.CloseWithError(err)
                                                return
                                        }
                                        basePos += uint(n)
                                        discard -= uint(n)
                                }
                                for discard > 0 {
                                        n, err := baseBuf.Discard(int(discard))
                                        if err != nil {
                                                _ = dstWr.CloseWithError(err)
                                                return
                                        }
                                        basePos += uint(n)
                                        discard -= uint(n)
                                }
                                if _, err := io.Copy(dstWr, io.LimitReader(baseBuf, int64(sz))); err != nil {
                                        _ = dstWr.CloseWithError(err)
                                        return
                                }
                                remainingTargetSz -= sz
                                basePos += sz

                        case isCopyFromDelta(cmd):
                                sz := uint(cmd) // cmd is the size itself
                                if invalidSize(sz, targetSz) {
                                        _ = dstWr.CloseWithError(ErrInvalidDelta)
                                        return
                                }
                                if _, err := io.Copy(dstWr, io.LimitReader(deltaBuf, int64(sz))); err != nil {
                                        _ = dstWr.CloseWithError(err)
                                        return
                                }

                                remainingTargetSz -= sz

                        default:
                                _ = dstWr.CloseWithError(ErrDeltaCmd)
                                return
                        }

                        if remainingTargetSz <= 0 {
                                _ = dstWr.Close()
                                return
                        }
                }
        }()

        return dstRd, nil
}

func patchDelta(dst *bytes.Buffer, src, delta []byte) error {
        if len(delta) < minCopySize {
                return ErrInvalidDelta
        }

        srcSz, delta := decodeLEB128(delta)
        if srcSz != uint(len(src)) {
                return ErrInvalidDelta
        }

        targetSz, delta := decodeLEB128(delta)
        remainingTargetSz := targetSz

        var cmd byte

        growSz := min(targetSz, maxPatchPreemptionSize)
        dst.Grow(int(growSz))
        for {
                if len(delta) == 0 {
                        return ErrInvalidDelta
                }

                cmd = delta[0]
                delta = delta[1:]

                switch {
                case isCopyFromSrc(cmd):
                        var offset, sz uint
                        var err error
                        offset, delta, err = decodeOffset(cmd, delta)
                        if err != nil {
                                return err
                        }

                        sz, delta, err = decodeSize(cmd, delta)
                        if err != nil {
                                return err
                        }

                        if invalidSize(sz, targetSz) ||
                                invalidOffsetSize(offset, sz, srcSz) {
                                break
                        }
                        dst.Write(src[offset : offset+sz])
                        remainingTargetSz -= sz

                case isCopyFromDelta(cmd):
                        sz := uint(cmd) // cmd is the size itself
                        if invalidSize(sz, targetSz) {
                                return ErrInvalidDelta
                        }

                        if uint(len(delta)) < sz {
                                return ErrInvalidDelta
                        }

                        dst.Write(delta[0:sz])
                        remainingTargetSz -= sz
                        delta = delta[sz:]

                default:
                        return ErrDeltaCmd
                }

                if remainingTargetSz <= 0 {
                        break
                }
        }

        return nil
}

func patchDeltaWriter(dst io.Writer, base io.ReaderAt, delta io.Reader,
        typ plumbing.ObjectType, writeHeader objectHeaderWriter,
) (uint, plumbing.Hash, error) {
        deltaBuf := bufio.NewReaderSize(delta, 1024)
        srcSz, err := decodeLEB128ByteReader(deltaBuf)
        if err != nil {
                if err == io.EOF {
                        return 0, plumbing.ZeroHash, ErrInvalidDelta
                }
                return 0, plumbing.ZeroHash, err
        }

        if r, ok := base.(*bytes.Reader); ok && srcSz != uint(r.Size()) {
                return 0, plumbing.ZeroHash, ErrInvalidDelta
        }

        targetSz, err := decodeLEB128ByteReader(deltaBuf)
        if err != nil {
                if err == io.EOF {
                        return 0, plumbing.ZeroHash, ErrInvalidDelta
                }
                return 0, plumbing.ZeroHash, err
        }

        // If header still needs to be written, caller will provide
        // a LazyObjectWriterHeader. This seems to be the case when
        // dealing with thin-packs.
        if writeHeader != nil {
                err = writeHeader(typ, int64(targetSz))
                if err != nil {
                        return 0, plumbing.ZeroHash, fmt.Errorf("could not lazy write header: %w", err)
                }
        }

        remainingTargetSz := targetSz

        hasher := plumbing.NewHasher(format.SHA1, typ, int64(targetSz))
        mw := io.MultiWriter(dst, hasher)

        bufp := sync.GetByteSlice()
        defer sync.PutByteSlice(bufp)

        sr := io.NewSectionReader(base, int64(0), int64(srcSz))
        // Keep both the io.LimitedReader types, so we can reset N.
        baselr := io.LimitReader(sr, 0).(*io.LimitedReader)
        deltalr := io.LimitReader(deltaBuf, 0).(*io.LimitedReader)

        for {
                buf := *bufp
                cmd, err := deltaBuf.ReadByte()
                if err == io.EOF {
                        return 0, plumbing.ZeroHash, ErrInvalidDelta
                }
                if err != nil {
                        return 0, plumbing.ZeroHash, err
                }

                if isCopyFromSrc(cmd) {
                        offset, err := decodeOffsetByteReader(cmd, deltaBuf)
                        if err != nil {
                                return 0, plumbing.ZeroHash, err
                        }
                        sz, err := decodeSizeByteReader(cmd, deltaBuf)
                        if err != nil {
                                return 0, plumbing.ZeroHash, err
                        }

                        if invalidSize(sz, targetSz) ||
                                invalidOffsetSize(offset, sz, srcSz) {
                                return 0, plumbing.ZeroHash, err
                        }

                        if _, err := sr.Seek(int64(offset), io.SeekStart); err != nil {
                                return 0, plumbing.ZeroHash, err
                        }
                        baselr.N = int64(sz)
                        if _, err := io.CopyBuffer(mw, baselr, buf); err != nil {
                                return 0, plumbing.ZeroHash, err
                        }
                        remainingTargetSz -= sz
                } else if isCopyFromDelta(cmd) {
                        sz := uint(cmd) // cmd is the size itself
                        if invalidSize(sz, targetSz) {
                                return 0, plumbing.ZeroHash, ErrInvalidDelta
                        }
                        deltalr.N = int64(sz)
                        if _, err := io.CopyBuffer(mw, deltalr, buf); err != nil {
                                return 0, plumbing.ZeroHash, err
                        }

                        remainingTargetSz -= sz
                } else {
                        return 0, plumbing.ZeroHash, err
                }
                if remainingTargetSz <= 0 {
                        break
                }
        }

        return targetSz, hasher.Sum(), nil
}

// Decodes a number encoded as an unsigned LEB128 at the start of some
// binary data and returns the decoded number and the rest of the
// stream.
//
// This must be called twice on the delta data buffer, first to get the
// expected source buffer size, and again to get the target buffer size.
func decodeLEB128(input []byte) (uint, []byte) {
        if len(input) == 0 {
                return 0, input
        }

        var num, sz uint
        var b byte
        for {
                b = input[sz]
                num |= (uint(b) & payload) << (sz * 7) // concats 7 bits chunks
                sz++

                if uint(b)&continuation == 0 || sz == uint(len(input)) {
                        break
                }
        }

        return num, input[sz:]
}

func decodeLEB128ByteReader(input io.ByteReader) (uint, error) {
        var num, sz uint
        for {
                b, err := input.ReadByte()
                if err != nil {
                        return 0, err
                }

                num |= (uint(b) & payload) << (sz * 7) // concats 7 bits chunks
                sz++

                if uint(b)&continuation == 0 {
                        break
                }
        }

        return num, nil
}

func isCopyFromSrc(cmd byte) bool {
        return (cmd & continuation) != 0
}

func isCopyFromDelta(cmd byte) bool {
        return (cmd&continuation) == 0 && cmd != 0
}

func decodeOffsetByteReader(cmd byte, delta io.ByteReader) (uint, error) {
        var offset uint
        for _, o := range offsets {
                if (cmd & o.mask) != 0 {
                        next, err := delta.ReadByte()
                        if err != nil {
                                return 0, err
                        }
                        offset |= uint(next) << o.shift
                }
        }

        return offset, nil
}

func decodeOffset(cmd byte, delta []byte) (uint, []byte, error) {
        var offset uint
        for _, o := range offsets {
                if (cmd & o.mask) != 0 {
                        if len(delta) == 0 {
                                return 0, nil, ErrInvalidDelta
                        }
                        offset |= uint(delta[0]) << o.shift
                        delta = delta[1:]
                }
        }

        return offset, delta, nil
}

func decodeSizeByteReader(cmd byte, delta io.ByteReader) (uint, error) {
        var sz uint
        for _, s := range sizes {
                if (cmd & s.mask) != 0 {
                        next, err := delta.ReadByte()
                        if err != nil {
                                return 0, err
                        }
                        sz |= uint(next) << s.shift
                }
        }

        if sz == 0 {
                sz = maxCopySize
        }

        return sz, nil
}

func decodeSize(cmd byte, delta []byte) (uint, []byte, error) {
        var sz uint
        for _, s := range sizes {
                if (cmd & s.mask) != 0 {
                        if len(delta) == 0 {
                                return 0, nil, ErrInvalidDelta
                        }
                        sz |= uint(delta[0]) << s.shift
                        delta = delta[1:]
                }
        }
        if sz == 0 {
                sz = maxCopySize
        }

        return sz, delta, nil
}

func invalidSize(sz, targetSz uint) bool {
        return sz > targetSz
}

func invalidOffsetSize(offset, sz, srcSz uint) bool {
        return sumOverflows(offset, sz) ||
                offset+sz > srcSz
}

func sumOverflows(a, b uint) bool {
        return a+b < a
}

package packfile

import (
        "bytes"
        "crypto"
        "encoding/hex"
        "fmt"

        "hash"
        "hash/crc32"
        "io"
        "sync"

        "github.com/go-git/go-git/v6/plumbing"
        format "github.com/go-git/go-git/v6/plumbing/format/config"
        gogithash "github.com/go-git/go-git/v6/plumbing/hash"
        "github.com/go-git/go-git/v6/plumbing/storer"
        "github.com/go-git/go-git/v6/utils/binary"
        gogitsync "github.com/go-git/go-git/v6/utils/sync"
)

var (
        // ErrEmptyPackfile is returned by ReadHeader when no data is found in the packfile.
        ErrEmptyPackfile = NewError("empty packfile")
        // ErrBadSignature is returned by ReadHeader when the signature in the packfile is incorrect.
        ErrBadSignature = NewError("malformed pack file signature")
        // ErrMalformedPackfile is returned when the packfile format is incorrect.
        ErrMalformedPackfile = NewError("malformed pack file")
        // ErrUnsupportedVersion is returned by ReadHeader when the packfile version is
        // different than VersionSupported.
        ErrUnsupportedVersion = NewError("unsupported packfile version")
        // ErrSeekNotSupported returned if seek is not support.
        ErrSeekNotSupported = NewError("not seek support")
)

// Scanner provides sequential access to the data stored in a Git packfile.
//
// A Git packfile is a compressed binary format that stores multiple Git objects,
// such as commits, trees, delta objects and blobs. These packfiles are used to
// reduce the size of data when transferring or storing Git repositories.
//
// A Git packfile is structured as follows:
//
//        +----------------------------------------------------+
//        |                 PACK File Header                   |
//        +----------------------------------------------------+
//        | "PACK"  | Version Number | Number of Objects       |
//        | (4 bytes)  |  (4 bytes)   |    (4 bytes)           |
//        +----------------------------------------------------+
//        |                  Object Entry #1                   |
//        +----------------------------------------------------+
//        |  Object Header  |  Compressed Object Data / Delta  |
//        | (type + size)   |  (var-length, zlib compressed)   |
//        +----------------------------------------------------+
//        |                         ...                        |
//        +----------------------------------------------------+
//        |                  PACK File Footer                  |
//        +----------------------------------------------------+
//        |                SHA-1 Checksum (20 bytes)           |
//        +----------------------------------------------------+
//
// For upstream docs, refer to https://git-scm.com/docs/gitformat-pack.
type Scanner struct {
        // version holds the packfile version.
        version Version
        // objects holds the quantiy of objects within the packfile.
        objects uint32
        // objIndex is the current index when going through the packfile objects.
        objIndex int
        // hasher is used to hash non-delta objects.
        hasher plumbing.Hasher
        // hasher256 is optional and used to hash the non-delta objects using SHA256.
        hasher256 *plumbing.Hasher
        // crc is used to generate the CRC-32 checksum of each object's content.
        crc hash.Hash32
        // packhash hashes the pack contents so that at the end it is able to
        // validate the packfile's footer checksum against the calculated hash.
        packhash gogithash.Hash
        // objectIdSize holds the object ID size.
        objectIDSize int

        // next holds what state function should be executed on the next
        // call to Scan().
        nextFn stateFn
        // packData holds the data for the last successful call to Scan().
        packData PackData
        // err holds the first error that occurred.
        err error

        m sync.Mutex

        // storage is optional, and when set is used to store full objects found.
        // Note that delta objects are not stored.
        storage storer.EncodedObjectStorer

        *scannerReader
        zr  gogitsync.ZLibReader
        buf bytes.Buffer
}

// NewScanner creates a new instance of Scanner.
func NewScanner(rs io.Reader, opts ...ScannerOption) *Scanner {
        dict := make([]byte, 16*1024)
        crc := crc32.NewIEEE()
        packhash := gogithash.New(crypto.SHA1)

        r := &Scanner{
                scannerReader: newScannerReader(rs, io.MultiWriter(crc, packhash)),
                zr:            gogitsync.NewZlibReader(&dict),
                objIndex:      -1,
                hasher:        plumbing.NewHasher(format.SHA1, plumbing.AnyObject, 0),
                crc:           crc,
                packhash:      packhash,
                nextFn:        packHeaderSignature,
                // Set the default size, which can be overriden by opts.
                objectIDSize: packhash.Size(),
        }

        for _, opt := range opts {
                opt(r)
        }

        return r
}

// Scan scans a Packfile sequently. Each call will navigate from a section
// to the next, until the entire file is read.
//
// The section data can be accessed via calls to Data(). Example:
//
//        for scanner.Scan() {
//            v := scanner.Data().Value()
//
//                switch scanner.Data().Section {
//                case HeaderSection:
//                        header := v.(Header)
//                        fmt.Println("[Header] Objects Qty:", header.ObjectsQty)
//                case ObjectSection:
//                        oh := v.(ObjectHeader)
//                        fmt.Println("[Object] Object Type:", oh.Type)
//                case FooterSection:
//                        checksum := v.(plumbing.Hash)
//                        fmt.Println("[Footer] Checksum:", checksum)
//                }
//        }
func (r *Scanner) Scan() bool {
        r.m.Lock()
        defer r.m.Unlock()

        if r.err != nil || r.nextFn == nil {
                return false
        }

        if err := scan(r); err != nil {
                r.err = err
                return false
        }

        return true
}

// Reset resets the current scanner, enabling it to be used to scan the
// same Packfile again.
func (r *Scanner) Reset() {
        r.scannerReader.Flush()
        r.scannerReader.Seek(0, io.SeekStart)
        r.packhash.Reset()

        r.objIndex = -1
        r.version = 0
        r.objects = 0
        r.packData = PackData{}
        r.err = nil
        r.nextFn = packHeaderSignature
}

// Data returns the pack data based on the last call to Scan().
func (r *Scanner) Data() PackData {
        return r.packData
}

// Data returns the first error that occurred on the last call to Scan().
// Once an error occurs, calls to Scan() becomes a no-op.
func (r *Scanner) Error() error {
        return r.err
}

func (r *Scanner) SeekFromStart(offset int64) error {
        r.Reset()

        if !r.Scan() {
                return fmt.Errorf("failed to reset and read header")
        }

        _, err := r.scannerReader.Seek(offset, io.SeekStart)
        return err
}

func (s *Scanner) WriteObject(oh *ObjectHeader, writer io.Writer) error {
        if oh.content.Len() > 0 {
                _, err := io.Copy(writer, bytes.NewReader(oh.content.Bytes()))
                return err
        }

        // If the oh is not an external ref and we don't have the
        // content offset, we won't be able to inflate via seeking through
        // the packfile.
        if oh.externalRef && oh.ContentOffset == 0 {
                return plumbing.ErrObjectNotFound
        }

        // Not a seeker data source.
        if s.seeker == nil {
                return plumbing.ErrObjectNotFound
        }

        err := s.inflateContent(oh.ContentOffset, writer)
        if err != nil {
                return ErrReferenceDeltaNotFound
        }

        return nil
}

func (s *Scanner) inflateContent(contentOffset int64, writer io.Writer) error {
        _, err := s.scannerReader.Seek(contentOffset, io.SeekStart)
        if err != nil {
                return err
        }

        err = s.zr.Reset(s.scannerReader)
        if err != nil {
                return fmt.Errorf("zlib reset error: %s", err)
        }

        _, err = io.Copy(writer, s.zr.Reader)
        if err != nil {
                return err
        }

        return nil
}

// scan goes through the next stateFn.
//
// State functions are chained by returning a non-nil value for stateFn.
// In such cases, the returned stateFn will be called immediately after
// the current func.
func scan(r *Scanner) error {
        var err error
        for state := r.nextFn; state != nil; {
                state, err = state(r)
                if err != nil {
                        return err
                }
        }
        return nil
}

// stateFn defines each individual state within the state machine that
// represents a packfile.
type stateFn func(*Scanner) (stateFn, error)

// packHeaderSignature validates the packfile's header signature and
// returns [ErrBadSignature] if the value provided is invalid.
//
// This is always the first state of a packfile and starts the chain
// that handles the entire packfile header.
func packHeaderSignature(r *Scanner) (stateFn, error) {
        start := make([]byte, 4)
        _, err := r.Read(start)
        if err != nil {
                return nil, fmt.Errorf("%w: %w", ErrBadSignature, err)
        }

        if bytes.Equal(start, signature) {
                return packVersion, nil
        }

        return nil, ErrBadSignature
}

// packVersion parses the packfile version. It returns [ErrMalformedPackfile]
// when the version cannot be parsed. If a valid version is parsed, but it is
// not currently supported, it returns [ErrUnsupportedVersion] instead.
func packVersion(r *Scanner) (stateFn, error) {
        version, err := binary.ReadUint32(r.scannerReader)
        if err != nil {
                return nil, fmt.Errorf("%w: cannot read version", ErrMalformedPackfile)
        }

        v := Version(version)
        if !v.Supported() {
                return nil, ErrUnsupportedVersion
        }

        r.version = v
        return packObjectsQty, nil
}

// packObjectsQty parses the quantity of objects that the packfile contains.
// If the value cannot be parsed, [ErrMalformedPackfile] is returned.
//
// This state ends the packfile header chain.
func packObjectsQty(r *Scanner) (stateFn, error) {
        qty, err := binary.ReadUint32(r.scannerReader)
        if err != nil {
                return nil, fmt.Errorf("%w: cannot read number of objects", ErrMalformedPackfile)
        }
        if qty == 0 {
                return packFooter, nil
        }

        r.objects = qty
        r.packData = PackData{
                Section: HeaderSection,
                header:  Header{Version: r.version, ObjectsQty: r.objects},
        }
        r.nextFn = objectEntry

        return nil, nil
}

// objectEntry handles the object entries within a packfile. This is generally
// split between object headers and their contents.
//
// The object header contains the object type and size. If the type cannot be parsed,
// [ErrMalformedPackfile] is returned.
//
// When SHA256 is enabled, the scanner will also calculate the SHA256 for each object.
func objectEntry(r *Scanner) (stateFn, error) {
        if r.objIndex+1 >= int(r.objects) {
                return packFooter, nil
        }
        r.objIndex++

        offset := r.scannerReader.offset

        r.scannerReader.Flush()
        r.crc.Reset()

        b := []byte{0}
        _, err := r.Read(b)
        if err != nil {
                return nil, err
        }

        typ := parseType(b[0])
        if !typ.Valid() {
                return nil, fmt.Errorf("%w: invalid object type: %v", ErrMalformedPackfile, b[0])
        }

        size, err := readVariableLengthSize(b[0], r)
        if err != nil {
                return nil, err
        }

        oh := ObjectHeader{
                Offset:   offset,
                Type:     typ,
                diskType: typ,
                Size:     int64(size),
        }

        switch oh.Type {
        case plumbing.OFSDeltaObject, plumbing.REFDeltaObject:
                // For delta objects, we need to skip the base reference
                if oh.Type == plumbing.OFSDeltaObject {
                        no, err := binary.ReadVariableWidthInt(r.scannerReader)
                        if err != nil {
                                return nil, err
                        }
                        oh.OffsetReference = oh.Offset - no
                } else {
                        oh.Reference.ResetBySize(r.objectIDSize)
                        _, err := oh.Reference.ReadFrom(r.scannerReader)
                        if err != nil {
                                return nil, err
                        }
                }
        }

        oh.ContentOffset = r.scannerReader.offset
        err = r.zr.Reset(r.scannerReader)
        if err != nil {
                return nil, fmt.Errorf("zlib reset error: %s", err)
        }

        if !oh.Type.IsDelta() {
                r.hasher.Reset(oh.Type, oh.Size)

                var mw io.Writer = r.hasher
                if r.storage != nil {
                        w, err := r.storage.RawObjectWriter(oh.Type, oh.Size)
                        if err != nil {
                                return nil, err
                        }

                        defer w.Close()
                        mw = io.MultiWriter(r.hasher, w)
                }

                if r.hasher256 != nil {
                        r.hasher256.Reset(oh.Type, oh.Size)
                        mw = io.MultiWriter(mw, r.hasher256)
                }

                // For non delta objects, simply calculate the hash of each object.
                _, err = io.CopyBuffer(mw, r.zr.Reader, r.buf.Bytes())
                if err != nil {
                        return nil, err
                }

                oh.Hash = r.hasher.Sum()
                if r.hasher256 != nil {
                        h := r.hasher256.Sum()
                        oh.Hash256 = &h
                }
        } else {
                // If data source is not io.Seeker, keep the content
                // in the cache, so that it can be accessed by the Parser.
                if r.scannerReader.seeker == nil {
                        _, err = oh.content.ReadFrom(r.zr.Reader)
                        if err != nil {
                                return nil, err
                        }
                } else {
                        // We don't know the compressed length, so we can't seek to
                        // the next object, we must discard the data instead.
                        _, err = io.Copy(io.Discard, r.zr.Reader)
                        if err != nil {
                                return nil, err
                        }
                }
        }
        r.scannerReader.Flush()
        oh.Crc32 = r.crc.Sum32()

        r.packData.Section = ObjectSection
        r.packData.objectHeader = oh

        return nil, nil
}

// packFooter parses the packfile checksum.
// If the checksum cannot be parsed, or it does not match the checksum
// calculated during the scanning process, an [ErrMalformedPackfile] is
// returned.
func packFooter(r *Scanner) (stateFn, error) {
        r.scannerReader.Flush()

        actual := r.packhash.Sum(nil)

        var checksum plumbing.Hash
        _, err := checksum.ReadFrom(r.scannerReader)
        if err != nil {
                return nil, fmt.Errorf("cannot read PACK checksum: %w", ErrMalformedPackfile)
        }

        if checksum.Compare(actual) != 0 {
                return nil, fmt.Errorf("checksum mismatch expected %q but found %q: %w",
                        hex.EncodeToString(actual), checksum, ErrMalformedPackfile)
        }

        r.packData.Section = FooterSection
        r.packData.checksum = checksum
        r.nextFn = nil

        return nil, nil
}

func readVariableLengthSize(first byte, reader io.ByteReader) (uint64, error) {
        // Extract the first part of the size (last 3 bits of the first byte).
        size := uint64(first & 0x0F)

        // |  001xxxx | xxxxxxxx | xxxxxxxx | ...
        //
        //         ^^^       ^^^^^^^^   ^^^^^^^^
        //        Type      Size Part 1   Size Part 2
        //
        // Check if more bytes are needed to fully determine the size.
        if first&maskContinue != 0 {
                shift := uint(4)

                for {
                        b, err := reader.ReadByte()
                        if err != nil {
                                return 0, err
                        }

                        // Add the next 7 bits to the size.
                        size |= uint64(b&0x7F) << shift

                        // Check if the continuation bit is set.
                        if b&maskContinue == 0 {
                                break
                        }

                        // Prepare for the next byte.
                        shift += 7
                }
        }
        return size, nil
}

func parseType(b byte) plumbing.ObjectType {
        return plumbing.ObjectType((b & maskType) >> firstLengthBits)
}

package packfile

import (
        "github.com/go-git/go-git/v6/plumbing"
        format "github.com/go-git/go-git/v6/plumbing/format/config"
)

type ScannerOption func(*Scanner)

// WithSHA256 enables the SHA256 hashing while scanning a pack file.
func WithSHA256() ScannerOption {
        return func(s *Scanner) {
                h := plumbing.NewHasher(format.SHA256, plumbing.AnyObject, 0)
                s.objectIDSize = format.SHA256Size
                s.hasher256 = &h
        }
}

package packfile

import (
        "bufio"
        "io"
)

// scannerReader has the following characteristics:
//   - Provides an io.SeekReader impl for bufio.Reader, when the underlying
//     reader supports it.
//   - Keeps track of the current read position, for when the underlying reader
//     isn't an io.SeekReader, but we still want to know the current offset.
//   - Writes to the hash writer what it reads, with the aid of a smaller buffer.
//     The buffer helps avoid a performance penalty for performing small writes
//     to the crc32 hash writer.
//
// Note that this is passed on to zlib, and it mmust support io.BytesReader, else
// it won't be able to just read the content of the current object, but rather it
// will read the entire packfile.
//
// scannerReader is not thread-safe.
type scannerReader struct {
        reader io.Reader
        crc    io.Writer
        rbuf   *bufio.Reader
        wbuf   *bufio.Writer
        offset int64
        seeker io.Seeker
}

func newScannerReader(r io.Reader, h io.Writer) *scannerReader {
        sr := &scannerReader{
                rbuf: bufio.NewReader(nil),
                wbuf: bufio.NewWriterSize(nil, 64),
                crc:  h,
        }
        sr.Reset(r)

        return sr
}

func (r *scannerReader) Reset(reader io.Reader) {
        r.reader = reader
        r.rbuf.Reset(r.reader)
        r.wbuf.Reset(r.crc)

        r.offset = 0

        seeker, ok := r.reader.(io.ReadSeeker)
        r.seeker = seeker

        if ok {
                r.offset, _ = seeker.Seek(0, io.SeekCurrent)
        }
}

func (r *scannerReader) Read(p []byte) (n int, err error) {
        n, err = r.rbuf.Read(p)

        r.offset += int64(n)
        if _, err := r.wbuf.Write(p[:n]); err != nil {
                return n, err
        }
        return
}

func (r *scannerReader) ReadByte() (b byte, err error) {
        b, err = r.rbuf.ReadByte()
        if err == nil {
                r.offset++
                return b, r.wbuf.WriteByte(b)
        }
        return
}

func (r *scannerReader) Flush() error {
        return r.wbuf.Flush()
}

// Seek seeks to a location. If the underlying reader is not an io.ReadSeeker,
// then only whence=io.SeekCurrent is supported, any other operation fails.
func (r *scannerReader) Seek(offset int64, whence int) (int64, error) {
        var err error

        if r.seeker == nil {
                if whence != io.SeekCurrent || offset != 0 {
                        return -1, ErrSeekNotSupported
                }
        }

        if whence == io.SeekCurrent && offset == 0 {
                return r.offset, nil
        }

        r.offset, err = r.seeker.Seek(offset, whence)
        r.rbuf.Reset(r.reader)

        return r.offset, err
}

package packfile

import (
        "bytes"

        "github.com/go-git/go-git/v6/plumbing"
)

type Version uint32

const (
        V2 Version = 2
)

func (v Version) Supported() bool {
        switch v {
        case V2:
                return true
        default:
                return false
        }
}

// ObjectHeader contains the information related to the object, this information
// is collected from the previous bytes to the content of the object.
type ObjectHeader struct {
        Type            plumbing.ObjectType
        Offset          int64
        ContentOffset   int64
        Size            int64
        Reference       plumbing.Hash
        OffsetReference int64
        Crc32           uint32
        Hash            plumbing.Hash
        Hash256         *plumbing.Hash

        content     bytes.Buffer
        parent      *ObjectHeader
        diskType    plumbing.ObjectType
        externalRef bool
}

// ID returns the preferred object ID.
func (oh *ObjectHeader) ID() plumbing.Hash {
        if oh.Hash256 != nil {
                return *oh.Hash256
        }
        return oh.Hash
}

type SectionType int

const (
        HeaderSection SectionType = iota
        ObjectSection
        FooterSection
)

type Header struct {
        Version    Version
        ObjectsQty uint32
}

type PackData struct {
        Section      SectionType
        header       Header
        objectHeader ObjectHeader
        checksum     plumbing.Hash
}

func (p PackData) Value() interface{} {
        switch p.Section {
        case HeaderSection:
                return p.header
        case ObjectSection:
                return p.objectHeader
        case FooterSection:
                return p.checksum
        default:
                return nil
        }
}

package object

import (
        "io"

        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/storer"
        "github.com/go-git/go-git/v6/utils/ioutil"
)

// Blob is used to store arbitrary data - it is generally a file.
type Blob struct {
        // Hash of the blob.
        Hash plumbing.Hash
        // Size of the (uncompressed) blob.
        Size int64

        obj plumbing.EncodedObject
}

// GetBlob gets a blob from an object storer and decodes it.
func GetBlob(s storer.EncodedObjectStorer, h plumbing.Hash) (*Blob, error) {
        o, err := s.EncodedObject(plumbing.BlobObject, h)
        if err != nil {
                return nil, err
        }

        return DecodeBlob(o)
}

// DecodeObject decodes an encoded object into a *Blob.
func DecodeBlob(o plumbing.EncodedObject) (*Blob, error) {
        b := &Blob{}
        if err := b.Decode(o); err != nil {
                return nil, err
        }

        return b, nil
}

// ID returns the object ID of the blob. The returned value will always match
// the current value of Blob.Hash.
//
// ID is present to fulfill the Object interface.
func (b *Blob) ID() plumbing.Hash {
        return b.Hash
}

// Type returns the type of object. It always returns plumbing.BlobObject.
//
// Type is present to fulfill the Object interface.
func (b *Blob) Type() plumbing.ObjectType {
        return plumbing.BlobObject
}

// Decode transforms a plumbing.EncodedObject into a Blob struct.
func (b *Blob) Decode(o plumbing.EncodedObject) error {
        if o.Type() != plumbing.BlobObject {
                return ErrUnsupportedObject
        }

        b.Hash = o.Hash()
        b.Size = o.Size()
        b.obj = o

        return nil
}

// Encode transforms a Blob into a plumbing.EncodedObject.
func (b *Blob) Encode(o plumbing.EncodedObject) (err error) {
        o.SetType(plumbing.BlobObject)

        w, err := o.Writer()
        if err != nil {
                return err
        }

        defer ioutil.CheckClose(w, &err)

        r, err := b.Reader()
        if err != nil {
                return err
        }

        defer ioutil.CheckClose(r, &err)

        _, err = io.Copy(w, r)
        return err
}

// Reader returns a reader allow the access to the content of the blob
func (b *Blob) Reader() (io.ReadCloser, error) {
        return b.obj.Reader()
}

// BlobIter provides an iterator for a set of blobs.
type BlobIter struct {
        storer.EncodedObjectIter
        s storer.EncodedObjectStorer
}

// NewBlobIter takes a storer.EncodedObjectStorer and a
// storer.EncodedObjectIter and returns a *BlobIter that iterates over all
// blobs contained in the storer.EncodedObjectIter.
//
// Any non-blob object returned by the storer.EncodedObjectIter is skipped.
func NewBlobIter(s storer.EncodedObjectStorer, iter storer.EncodedObjectIter) *BlobIter {
        return &BlobIter{iter, s}
}

// Next moves the iterator to the next blob and returns a pointer to it. If
// there are no more blobs, it returns io.EOF.
func (iter *BlobIter) Next() (*Blob, error) {
        for {
                obj, err := iter.EncodedObjectIter.Next()
                if err != nil {
                        return nil, err
                }

                if obj.Type() != plumbing.BlobObject {
                        continue
                }

                return DecodeBlob(obj)
        }
}

// ForEach call the cb function for each blob contained on this iter until
// an error happens or the end of the iter is reached. If ErrStop is sent
// the iteration is stop but no error is returned. The iterator is closed.
func (iter *BlobIter) ForEach(cb func(*Blob) error) error {
        return iter.EncodedObjectIter.ForEach(func(obj plumbing.EncodedObject) error {
                if obj.Type() != plumbing.BlobObject {
                        return nil
                }

                b, err := DecodeBlob(obj)
                if err != nil {
                        return err
                }

                return cb(b)
        })
}

package object

import (
        "bytes"
        "context"
        "fmt"
        "strings"

        "github.com/go-git/go-git/v6/utils/merkletrie"
)

// Change values represent a detected change between two git trees.  For
// modifications, From is the original status of the node and To is its
// final status.  For insertions, From is the zero value and for
// deletions To is the zero value.
type Change struct {
        From ChangeEntry
        To   ChangeEntry
}

var empty ChangeEntry

// Action returns the kind of action represented by the change, an
// insertion, a deletion or a modification.
func (c *Change) Action() (merkletrie.Action, error) {
        if c.From == empty && c.To == empty {
                return merkletrie.Action(0),
                        fmt.Errorf("malformed change: empty from and to")
        }

        if c.From == empty {
                return merkletrie.Insert, nil
        }

        if c.To == empty {
                return merkletrie.Delete, nil
        }

        return merkletrie.Modify, nil
}

// Files returns the files before and after a change.
// For insertions from will be nil. For deletions to will be nil.
func (c *Change) Files() (from, to *File, err error) {
        action, err := c.Action()
        if err != nil {
                return
        }

        if action == merkletrie.Insert || action == merkletrie.Modify {
                to, err = c.To.Tree.TreeEntryFile(&c.To.TreeEntry)
                if !c.To.TreeEntry.Mode.IsFile() {
                        return nil, nil, nil
                }

                if err != nil {
                        return
                }
        }

        if action == merkletrie.Delete || action == merkletrie.Modify {
                from, err = c.From.Tree.TreeEntryFile(&c.From.TreeEntry)
                if !c.From.TreeEntry.Mode.IsFile() {
                        return nil, nil, nil
                }

                if err != nil {
                        return
                }
        }

        return
}

func (c *Change) String() string {
        action, err := c.Action()
        if err != nil {
                return "malformed change"
        }

        return fmt.Sprintf("<Action: %s, Path: %s>", action, c.name())
}

// Patch returns a Patch with all the file changes in chunks. This
// representation can be used to create several diff outputs.
func (c *Change) Patch() (*Patch, error) {
        return c.PatchContext(context.Background())
}

// Patch returns a Patch with all the file changes in chunks. This
// representation can be used to create several diff outputs.
// If context expires, an non-nil error will be returned
// Provided context must be non-nil
func (c *Change) PatchContext(ctx context.Context) (*Patch, error) {
        return getPatchContext(ctx, "", c)
}

func (c *Change) name() string {
        if c.From != empty {
                return c.From.Name
        }

        return c.To.Name
}

// ChangeEntry values represent a node that has suffered a change.
type ChangeEntry struct {
        // Full path of the node using "/" as separator.
        Name string
        // Parent tree of the node that has changed.
        Tree *Tree
        // The entry of the node.
        TreeEntry TreeEntry
}

// Changes represents a collection of changes between two git trees.
// Implements sort.Interface lexicographically over the path of the
// changed files.
type Changes []*Change

func (c Changes) Len() int {
        return len(c)
}

func (c Changes) Swap(i, j int) {
        c[i], c[j] = c[j], c[i]
}

func (c Changes) Less(i, j int) bool {
        return strings.Compare(c[i].name(), c[j].name()) < 0
}

func (c Changes) String() string {
        var buffer bytes.Buffer
        buffer.WriteString("[")
        comma := ""
        for _, v := range c {
                buffer.WriteString(comma)
                buffer.WriteString(v.String())
                comma = ", "
        }
        buffer.WriteString("]")

        return buffer.String()
}

// Patch returns a Patch with all the changes in chunks. This
// representation can be used to create several diff outputs.
func (c Changes) Patch() (*Patch, error) {
        return c.PatchContext(context.Background())
}

// Patch returns a Patch with all the changes in chunks. This
// representation can be used to create several diff outputs.
// If context expires, an non-nil error will be returned
// Provided context must be non-nil
func (c Changes) PatchContext(ctx context.Context) (*Patch, error) {
        return getPatchContext(ctx, "", c...)
}

package object

import (
        "errors"
        "fmt"

        "github.com/go-git/go-git/v6/utils/merkletrie"
        "github.com/go-git/go-git/v6/utils/merkletrie/noder"
)

// The following functions transform changes types form the merkletrie
// package to changes types from this package.

func newChange(c merkletrie.Change) (*Change, error) {
        ret := &Change{}

        var err error
        if ret.From, err = newChangeEntry(c.From); err != nil {
                return nil, fmt.Errorf("from field: %s", err)
        }

        if ret.To, err = newChangeEntry(c.To); err != nil {
                return nil, fmt.Errorf("to field: %s", err)
        }

        return ret, nil
}

func newChangeEntry(p noder.Path) (ChangeEntry, error) {
        if p == nil {
                return empty, nil
        }

        asTreeNoder, ok := p.Last().(*treeNoder)
        if !ok {
                return ChangeEntry{}, errors.New("cannot transform non-TreeNoders")
        }

        return ChangeEntry{
                Name: p.String(),
                Tree: asTreeNoder.parent,
                TreeEntry: TreeEntry{
                        Name: asTreeNoder.name,
                        Mode: asTreeNoder.mode,
                        Hash: asTreeNoder.hash,
                },
        }, nil
}

func newChanges(src merkletrie.Changes) (Changes, error) {
        ret := make(Changes, len(src))
        var err error
        for i, e := range src {
                ret[i], err = newChange(e)
                if err != nil {
                        return nil, fmt.Errorf("change #%d: %s", i, err)
                }
        }

        return ret, nil
}

package object

import (
        "bytes"
        "context"
        "errors"
        "fmt"
        "io"
        "strings"

        "github.com/ProtonMail/go-crypto/openpgp"

        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/storer"
        "github.com/go-git/go-git/v6/utils/ioutil"
        "github.com/go-git/go-git/v6/utils/sync"
)

const (
        beginpgp       string = "-----BEGIN PGP SIGNATURE-----"
        endpgp         string = "-----END PGP SIGNATURE-----"
        headerpgp      string = "gpgsig"
        headerencoding string = "encoding"

        // https://github.com/git/git/blob/bcb6cae2966cc407ca1afc77413b3ef11103c175/Documentation/gitformat-signature.txt#L153
        // When a merge commit is created from a signed tag, the tag is embedded in
        // the commit with the "mergetag" header.
        headermergetag string = "mergetag"

        defaultUtf8CommitMessageEncoding MessageEncoding = "UTF-8"
)

// Hash represents the hash of an object
type Hash plumbing.Hash

// MessageEncoding represents the encoding of a commit
type MessageEncoding string

// Commit points to a single tree, marking it as what the project looked like
// at a certain point in time. It contains meta-information about that point
// in time, such as a timestamp, the author of the changes since the last
// commit, a pointer to the previous commit(s), etc.
// http://shafiulazam.com/gitbook/1_the_git_object_model.html
type Commit struct {
        // Hash of the commit object.
        Hash plumbing.Hash
        // Author is the original author of the commit.
        Author Signature
        // Committer is the one performing the commit, might be different from
        // Author.
        Committer Signature
        // MergeTag is the embedded tag object when a merge commit is created by
        // merging a signed tag.
        MergeTag string
        // PGPSignature is the PGP signature of the commit.
        PGPSignature string
        // Message is the commit message, contains arbitrary text.
        Message string
        // TreeHash is the hash of the root tree of the commit.
        TreeHash plumbing.Hash
        // ParentHashes are the hashes of the parent commits of the commit.
        ParentHashes []plumbing.Hash
        // Encoding is the encoding of the commit.
        Encoding MessageEncoding

        s storer.EncodedObjectStorer
}

// GetCommit gets a commit from an object storer and decodes it.
func GetCommit(s storer.EncodedObjectStorer, h plumbing.Hash) (*Commit, error) {
        o, err := s.EncodedObject(plumbing.CommitObject, h)
        if err != nil {
                return nil, err
        }

        return DecodeCommit(s, o)
}

// DecodeCommit decodes an encoded object into a *Commit and associates it to
// the given object storer.
func DecodeCommit(s storer.EncodedObjectStorer, o plumbing.EncodedObject) (*Commit, error) {
        c := &Commit{s: s}
        if err := c.Decode(o); err != nil {
                return nil, err
        }

        return c, nil
}

// Tree returns the Tree from the commit.
func (c *Commit) Tree() (*Tree, error) {
        return GetTree(c.s, c.TreeHash)
}

// PatchContext returns the Patch between the actual commit and the provided one.
// Error will be return if context expires. Provided context must be non-nil.
//
// NOTE: Since version 5.1.0 the renames are correctly handled, the settings
// used are the recommended options DefaultDiffTreeOptions.
func (c *Commit) PatchContext(ctx context.Context, to *Commit) (*Patch, error) {
        fromTree, err := c.Tree()
        if err != nil {
                return nil, err
        }

        var toTree *Tree
        if to != nil {
                toTree, err = to.Tree()
                if err != nil {
                        return nil, err
                }
        }

        return fromTree.PatchContext(ctx, toTree)
}

// Patch returns the Patch between the actual commit and the provided one.
//
// NOTE: Since version 5.1.0 the renames are correctly handled, the settings
// used are the recommended options DefaultDiffTreeOptions.
func (c *Commit) Patch(to *Commit) (*Patch, error) {
        return c.PatchContext(context.Background(), to)
}

// Parents return a CommitIter to the parent Commits.
func (c *Commit) Parents() CommitIter {
        return NewCommitIter(c.s,
                storer.NewEncodedObjectLookupIter(c.s, plumbing.CommitObject, c.ParentHashes),
        )
}

// NumParents returns the number of parents in a commit.
func (c *Commit) NumParents() int {
        return len(c.ParentHashes)
}

var ErrParentNotFound = errors.New("commit parent not found")

// Parent returns the ith parent of a commit.
func (c *Commit) Parent(i int) (*Commit, error) {
        if len(c.ParentHashes) == 0 || i > len(c.ParentHashes)-1 {
                return nil, ErrParentNotFound
        }

        return GetCommit(c.s, c.ParentHashes[i])
}

// File returns the file with the specified "path" in the commit and a
// nil error if the file exists. If the file does not exist, it returns
// a nil file and the ErrFileNotFound error.
func (c *Commit) File(path string) (*File, error) {
        tree, err := c.Tree()
        if err != nil {
                return nil, err
        }

        return tree.File(path)
}

// Files returns a FileIter allowing to iterate over the Tree
func (c *Commit) Files() (*FileIter, error) {
        tree, err := c.Tree()
        if err != nil {
                return nil, err
        }

        return tree.Files(), nil
}

// ID returns the object ID of the commit. The returned value will always match
// the current value of Commit.Hash.
//
// ID is present to fulfill the Object interface.
func (c *Commit) ID() plumbing.Hash {
        return c.Hash
}

// Type returns the type of object. It always returns plumbing.CommitObject.
//
// Type is present to fulfill the Object interface.
func (c *Commit) Type() plumbing.ObjectType {
        return plumbing.CommitObject
}

// Decode transforms a plumbing.EncodedObject into a Commit struct.
func (c *Commit) Decode(o plumbing.EncodedObject) (err error) {
        if o.Type() != plumbing.CommitObject {
                return ErrUnsupportedObject
        }

        c.Hash = o.Hash()
        c.Encoding = defaultUtf8CommitMessageEncoding

        reader, err := o.Reader()
        if err != nil {
                return err
        }
        defer ioutil.CheckClose(reader, &err)

        r := sync.GetBufioReader(reader)
        defer sync.PutBufioReader(r)

        var message bool
        var mergetag bool
        var pgpsig bool
        var msgbuf bytes.Buffer
        for {
                line, err := r.ReadBytes('\n')
                if err != nil && err != io.EOF {
                        return err
                }

                if mergetag {
                        if len(line) > 0 && line[0] == ' ' {
                                line = bytes.TrimLeft(line, " ")
                                c.MergeTag += string(line)
                                continue
                        } else {
                                mergetag = false
                        }
                }

                if pgpsig {
                        if len(line) > 0 && line[0] == ' ' {
                                line = bytes.TrimLeft(line, " ")
                                c.PGPSignature += string(line)
                                continue
                        } else {
                                pgpsig = false
                        }
                }

                if !message {
                        line = bytes.TrimSpace(line)
                        if len(line) == 0 {
                                message = true
                                continue
                        }

                        split := bytes.SplitN(line, []byte{' '}, 2)

                        var data []byte
                        if len(split) == 2 {
                                data = split[1]
                        }

                        switch string(split[0]) {
                        case "tree":
                                c.TreeHash = plumbing.NewHash(string(data))
                        case "parent":
                                c.ParentHashes = append(c.ParentHashes, plumbing.NewHash(string(data)))
                        case "author":
                                c.Author.Decode(data)
                        case "committer":
                                c.Committer.Decode(data)
                        case headermergetag:
                                c.MergeTag += string(data) + "\n"
                                mergetag = true
                        case headerencoding:
                                c.Encoding = MessageEncoding(data)
                        case headerpgp:
                                c.PGPSignature += string(data) + "\n"
                                pgpsig = true
                        }
                } else {
                        msgbuf.Write(line)
                }

                if err == io.EOF {
                        break
                }
        }
        c.Message = msgbuf.String()
        return nil
}

// Encode transforms a Commit into a plumbing.EncodedObject.
func (c *Commit) Encode(o plumbing.EncodedObject) error {
        return c.encode(o, true)
}

// EncodeWithoutSignature export a Commit into a plumbing.EncodedObject without the signature (correspond to the payload of the PGP signature).
func (c *Commit) EncodeWithoutSignature(o plumbing.EncodedObject) error {
        return c.encode(o, false)
}

func (c *Commit) encode(o plumbing.EncodedObject, includeSig bool) (err error) {
        o.SetType(plumbing.CommitObject)
        w, err := o.Writer()
        if err != nil {
                return err
        }

        defer ioutil.CheckClose(w, &err)

        if _, err = fmt.Fprintf(w, "tree %s\n", c.TreeHash.String()); err != nil {
                return err
        }

        for _, parent := range c.ParentHashes {
                if _, err = fmt.Fprintf(w, "parent %s\n", parent.String()); err != nil {
                        return err
                }
        }

        if _, err = fmt.Fprint(w, "author "); err != nil {
                return err
        }

        if err = c.Author.Encode(w); err != nil {
                return err
        }

        if _, err = fmt.Fprint(w, "\ncommitter "); err != nil {
                return err
        }

        if err = c.Committer.Encode(w); err != nil {
                return err
        }

        if c.MergeTag != "" {
                if _, err = fmt.Fprint(w, "\n"+headermergetag+" "); err != nil {
                        return err
                }

                // Split tag information lines and re-write with a left padding and
                // newline. Use join for this so it's clear that a newline should not be
                // added after this section. The newline will be added either as part of
                // the PGP signature or the commit message.
                mergetag := strings.TrimSuffix(c.MergeTag, "\n")
                lines := strings.Split(mergetag, "\n")
                if _, err = fmt.Fprint(w, strings.Join(lines, "\n ")); err != nil {
                        return err
                }
        }

        if string(c.Encoding) != "" && c.Encoding != defaultUtf8CommitMessageEncoding {
                if _, err = fmt.Fprintf(w, "\n%s %s", headerencoding, c.Encoding); err != nil {
                        return err
                }
        }

        if c.PGPSignature != "" && includeSig {
                if _, err = fmt.Fprint(w, "\n"+headerpgp+" "); err != nil {
                        return err
                }

                // Split all the signature lines and re-write with a left padding and
                // newline. Use join for this so it's clear that a newline should not be
                // added after this section, as it will be added when the message is
                // printed.
                signature := strings.TrimSuffix(c.PGPSignature, "\n")
                lines := strings.Split(signature, "\n")
                if _, err = fmt.Fprint(w, strings.Join(lines, "\n ")); err != nil {
                        return err
                }
        }

        if _, err = fmt.Fprintf(w, "\n\n%s", c.Message); err != nil {
                return err
        }

        return err
}

// Stats returns the stats of a commit.
func (c *Commit) Stats() (FileStats, error) {
        return c.StatsContext(context.Background())
}

// StatsContext returns the stats of a commit. Error will be return if context
// expires. Provided context must be non-nil.
func (c *Commit) StatsContext(ctx context.Context) (FileStats, error) {
        fromTree, err := c.Tree()
        if err != nil {
                return nil, err
        }

        toTree := &Tree{}
        if c.NumParents() != 0 {
                firstParent, err := c.Parents().Next()
                if err != nil {
                        return nil, err
                }

                toTree, err = firstParent.Tree()
                if err != nil {
                        return nil, err
                }
        }

        patch, err := toTree.PatchContext(ctx, fromTree)
        if err != nil {
                return nil, err
        }

        return getFileStatsFromFilePatches(patch.FilePatches()), nil
}

func (c *Commit) String() string {
        return fmt.Sprintf(
                "%s %s\nAuthor: %s\nDate:   %s\n\n%s\n",
                plumbing.CommitObject, c.Hash, c.Author.String(),
                c.Author.When.Format(DateFormat), indent(c.Message),
        )
}

// Verify performs PGP verification of the commit with a provided armored
// keyring and returns openpgp.Entity associated with verifying key on success.
func (c *Commit) Verify(armoredKeyRing string) (*openpgp.Entity, error) {
        keyRingReader := strings.NewReader(armoredKeyRing)
        keyring, err := openpgp.ReadArmoredKeyRing(keyRingReader)
        if err != nil {
                return nil, err
        }

        // Extract signature.
        signature := strings.NewReader(c.PGPSignature)

        encoded := &plumbing.MemoryObject{}
        // Encode commit components, excluding signature and get a reader object.
        if err := c.EncodeWithoutSignature(encoded); err != nil {
                return nil, err
        }
        er, err := encoded.Reader()
        if err != nil {
                return nil, err
        }

        return openpgp.CheckArmoredDetachedSignature(keyring, er, signature, nil)
}

// Less defines a compare function to determine which commit is 'earlier' by:
// - First use Committer.When
// - If Committer.When are equal then use Author.When
// - If Author.When also equal then compare the string value of the hash
func (c *Commit) Less(rhs *Commit) bool {
        return c.Committer.When.Before(rhs.Committer.When) ||
                (c.Committer.When.Equal(rhs.Committer.When) &&
                        (c.Author.When.Before(rhs.Author.When) ||
                                (c.Author.When.Equal(rhs.Author.When) && c.Hash.Compare(rhs.Hash.Bytes()) < 0)))
}

func indent(t string) string {
        var output []string
        for _, line := range strings.Split(t, "\n") {
                if len(line) != 0 {
                        line = "    " + line
                }

                output = append(output, line)
        }

        return strings.Join(output, "\n")
}

// CommitIter is a generic closable interface for iterating over commits.
type CommitIter interface {
        Next() (*Commit, error)
        ForEach(func(*Commit) error) error
        Close()
}

// storerCommitIter provides an iterator from commits in an EncodedObjectStorer.
type storerCommitIter struct {
        storer.EncodedObjectIter
        s storer.EncodedObjectStorer
}

// NewCommitIter takes a storer.EncodedObjectStorer and a
// storer.EncodedObjectIter and returns a CommitIter that iterates over all
// commits contained in the storer.EncodedObjectIter.
//
// Any non-commit object returned by the storer.EncodedObjectIter is skipped.
func NewCommitIter(s storer.EncodedObjectStorer, iter storer.EncodedObjectIter) CommitIter {
        return &storerCommitIter{iter, s}
}

// Next moves the iterator to the next commit and returns a pointer to it. If
// there are no more commits, it returns io.EOF.
func (iter *storerCommitIter) Next() (*Commit, error) {
        obj, err := iter.EncodedObjectIter.Next()
        if err != nil {
                return nil, err
        }

        return DecodeCommit(iter.s, obj)
}

// ForEach call the cb function for each commit contained on this iter until
// an error appends or the end of the iter is reached. If ErrStop is sent
// the iteration is stopped but no error is returned. The iterator is closed.
func (iter *storerCommitIter) ForEach(cb func(*Commit) error) error {
        return iter.EncodedObjectIter.ForEach(func(obj plumbing.EncodedObject) error {
                c, err := DecodeCommit(iter.s, obj)
                if err != nil {
                        return err
                }

                return cb(c)
        })
}

func (iter *storerCommitIter) Close() {
        iter.EncodedObjectIter.Close()
}

package object

import (
        "container/list"
        "errors"
        "io"

        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/storer"
        "github.com/go-git/go-git/v6/storage"
)

type commitPreIterator struct {
        seenExternal map[plumbing.Hash]bool
        seen         map[plumbing.Hash]bool
        stack        []CommitIter
        start        *Commit
}


func forEachCommit(next func() (*Commit, error), cb func(*Commit) error) error {
        for {
                c, err := next()
                if errors.Is(err, io.EOF) {
                        break
                }
                if err != nil {
                        return err
                }

                err = cb(c)
                if err == storer.ErrStop {
                        break
                }
                if err != nil {
                        return err
                }
        }
        return nil
}

// NewCommitPreorderIter returns a CommitIter that walks the commit history,
// starting at the given commit and visiting its parents in pre-order.
// The given callback will be called for each visited commit. Each commit will
// be visited only once. If the callback returns an error, walking will stop
// and will return the error. Other errors might be returned if the history
// cannot be traversed (e.g. missing objects). Ignore allows to skip some
// commits from being iterated.
func NewCommitPreorderIter(
        c *Commit,
        seenExternal map[plumbing.Hash]bool,
        ignore []plumbing.Hash,
) CommitIter {
        seen := make(map[plumbing.Hash]bool)
        for _, h := range ignore {
                seen[h] = true
        }

        return &commitPreIterator{
                seenExternal: seenExternal,
                seen:         seen,
                stack:        make([]CommitIter, 0),
                start:        c,
        }
}

func (w *commitPreIterator) Next() (*Commit, error) {
        var c *Commit
        for {
                if w.start != nil {
                        c = w.start
                        w.start = nil
                } else {
                        current := len(w.stack) - 1
                        if current < 0 {
                                return nil, io.EOF
                        }

                        var err error
                        c, err = w.stack[current].Next()
                        if err == io.EOF {
                                w.stack = w.stack[:current]
                                continue
                        }

                        if err != nil {
                                return nil, err
                        }
                }

                if w.seen[c.Hash] || w.seenExternal[c.Hash] {
                        continue
                }

                w.seen[c.Hash] = true

                if c.NumParents() > 0 {
                        w.stack = append(w.stack, filteredParentIter(c, w.seen))
                }

                return c, nil
        }
}

func filteredParentIter(c *Commit, seen map[plumbing.Hash]bool) CommitIter {
        var hashes []plumbing.Hash
        for _, h := range c.ParentHashes {
                if !seen[h] {
                        hashes = append(hashes, h)
                }
        }

        return NewCommitIter(c.s,
                storer.NewEncodedObjectLookupIter(c.s, plumbing.CommitObject, hashes),
        )
}

func (w *commitPreIterator) ForEach(cb func(*Commit) error) error {
        return forEachCommit(w.Next, cb)
}

func (w *commitPreIterator) Close() {}

type commitPostIterator struct {
        stack []*Commit
        seen  map[plumbing.Hash]bool
}

// NewCommitPostorderIter returns a CommitIter that walks the commit
// history like WalkCommitHistory but in post-order. This means that after
// walking a merge commit, the merged commit will be walked before the base
// it was merged on. This can be useful if you wish to see the history in
// chronological order. Ignore allows to skip some commits from being iterated.
func NewCommitPostorderIter(c *Commit, ignore []plumbing.Hash) CommitIter {
        seen := make(map[plumbing.Hash]bool)
        for _, h := range ignore {
                seen[h] = true
        }

        return &commitPostIterator{
                stack: []*Commit{c},
                seen:  seen,
        }
}

func (w *commitPostIterator) Next() (*Commit, error) {
        for {
                if len(w.stack) == 0 {
                        return nil, io.EOF
                }

                c := w.stack[len(w.stack)-1]
                w.stack = w.stack[:len(w.stack)-1]

                if w.seen[c.Hash] {
                        continue
                }

                w.seen[c.Hash] = true

                return c, c.Parents().ForEach(func(p *Commit) error {
                        w.stack = append(w.stack, p)
                        return nil
                })
        }
}

func (w *commitPostIterator) ForEach(cb func(*Commit) error) error {
        return forEachCommit(w.Next, cb)
}

func (w *commitPostIterator) Close() {}

type commitPostIteratorFirstParent struct {
        stack []*Commit
        seen  map[plumbing.Hash]bool
}

// NewCommitPostorderIterFirstParent returns a CommitIter that walks the commit
// history like WalkCommitHistory but in post-order.
//
// This option acts like the git log --first-parent flag, skipping intermediate
// commits that were brought in via a merge commit.
// Ignore allows to skip some commits from being iterated.
func NewCommitPostorderIterFirstParent(c *Commit, ignore []plumbing.Hash) CommitIter {
        seen := make(map[plumbing.Hash]bool)
        for _, h := range ignore {
                seen[h] = true
        }

        return &commitPostIteratorFirstParent{
                stack: []*Commit{c},
                seen:  seen,
        }
}

func (w *commitPostIteratorFirstParent) Next() (*Commit, error) {
        for {
                if len(w.stack) == 0 {
                        return nil, io.EOF
                }

                c := w.stack[len(w.stack)-1]
                w.stack = w.stack[:len(w.stack)-1]

                if w.seen[c.Hash] {
                        continue
                }

                w.seen[c.Hash] = true

                return c, c.Parents().ForEach(func(p *Commit) error {
                        if len(c.ParentHashes) > 0 && p.Hash == c.ParentHashes[0] {
                                w.stack = append(w.stack, p)
                        }
                        return nil
                })
        }
}

func (w *commitPostIteratorFirstParent) ForEach(cb func(*Commit) error) error {
        return forEachCommit(w.Next, cb)
}

func (w *commitPostIteratorFirstParent) Close() {}

// commitAllIterator stands for commit iterator for all refs.
type commitAllIterator struct {
        // currCommit points to the current commit.
        currCommit *list.Element
}

// NewCommitAllIter returns a new commit iterator for all refs.
// repoStorer is a repo Storer used to get commits and references.
// commitIterFunc is a commit iterator function, used to iterate through ref commits in chosen order
func NewCommitAllIter(repoStorer storage.Storer, commitIterFunc func(*Commit) CommitIter) (CommitIter, error) {
        commitsPath := list.New()
        commitsLookup := make(map[plumbing.Hash]*list.Element)
        head, err := storer.ResolveReference(repoStorer, plumbing.HEAD)
        if err == nil {
                err = addReference(repoStorer, commitIterFunc, head, commitsPath, commitsLookup)
        }

        if err != nil && err != plumbing.ErrReferenceNotFound {
                return nil, err
        }

        // add all references along with the HEAD
        refIter, err := repoStorer.IterReferences()
        if err != nil {
                return nil, err
        }
        defer refIter.Close()

        for {
                ref, err := refIter.Next()
                if err == io.EOF {
                        break
                }

                if err == plumbing.ErrReferenceNotFound {
                        continue
                }

                if err != nil {
                        return nil, err
                }

                if err = addReference(repoStorer, commitIterFunc, ref, commitsPath, commitsLookup); err != nil {
                        return nil, err
                }
        }

        return &commitAllIterator{commitsPath.Front()}, nil
}

func addReference(
        repoStorer storage.Storer,
        commitIterFunc func(*Commit) CommitIter,
        ref *plumbing.Reference,
        commitsPath *list.List,
        commitsLookup map[plumbing.Hash]*list.Element) error {

        _, exists := commitsLookup[ref.Hash()]
        if exists {
                // we already have it - skip the reference.
                return nil
        }

        refCommit, _ := GetCommit(repoStorer, ref.Hash())
        if refCommit == nil {
                // if it's not a commit - skip it.
                return nil
        }

        var (
                refCommits []*Commit
                parent     *list.Element
        )
        // collect all ref commits to add
        commitIter := commitIterFunc(refCommit)
        for c, e := commitIter.Next(); e == nil; {
                parent, exists = commitsLookup[c.Hash]
                if exists {
                        break
                }
                refCommits = append(refCommits, c)
                c, e = commitIter.Next()
        }
        commitIter.Close()

        if parent == nil {
                // common parent - not found
                // add all commits to the path from this ref (maybe it's a HEAD and we don't have anything, yet)
                for _, c := range refCommits {
                        parent = commitsPath.PushBack(c)
                        commitsLookup[c.Hash] = parent
                }
        } else {
                // add ref's commits to the path in reverse order (from the latest)
                for i := len(refCommits) - 1; i >= 0; i-- {
                        c := refCommits[i]
                        // insert before found common parent
                        parent = commitsPath.InsertBefore(c, parent)
                        commitsLookup[c.Hash] = parent
                }
        }

        return nil
}

func (it *commitAllIterator) Next() (*Commit, error) {
        if it.currCommit == nil {
                return nil, io.EOF
        }

        c := it.currCommit.Value.(*Commit)
        it.currCommit = it.currCommit.Next()

        return c, nil
}

func (it *commitAllIterator) ForEach(cb func(*Commit) error) error {
        return forEachCommit(it.Next, cb)
}

func (it *commitAllIterator) Close() {
        it.currCommit = nil
}

package object

import (
        "io"

        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/storer"
)

type bfsCommitIterator struct {
        seenExternal map[plumbing.Hash]bool
        seen         map[plumbing.Hash]bool
        queue        []*Commit
}

// NewCommitIterBSF returns a CommitIter that walks the commit history,
// starting at the given commit and visiting its parents in pre-order.
// The given callback will be called for each visited commit. Each commit will
// be visited only once. If the callback returns an error, walking will stop
// and will return the error. Other errors might be returned if the history
// cannot be traversed (e.g. missing objects). Ignore allows to skip some
// commits from being iterated.
func NewCommitIterBSF(
        c *Commit,
        seenExternal map[plumbing.Hash]bool,
        ignore []plumbing.Hash,
) CommitIter {
        seen := make(map[plumbing.Hash]bool)
        for _, h := range ignore {
                seen[h] = true
        }

        return &bfsCommitIterator{
                seenExternal: seenExternal,
                seen:         seen,
                queue:        []*Commit{c},
        }
}

func (w *bfsCommitIterator) appendHash(store storer.EncodedObjectStorer, h plumbing.Hash) error {
        if w.seen[h] || w.seenExternal[h] {
                return nil
        }
        c, err := GetCommit(store, h)
        if err != nil {
                return err
        }
        w.queue = append(w.queue, c)
        return nil
}

func (w *bfsCommitIterator) Next() (*Commit, error) {
        var c *Commit
        for {
                if len(w.queue) == 0 {
                        return nil, io.EOF
                }
                c = w.queue[0]
                w.queue = w.queue[1:]

                if w.seen[c.Hash] || w.seenExternal[c.Hash] {
                        continue
                }

                w.seen[c.Hash] = true

                for _, h := range c.ParentHashes {
                        err := w.appendHash(c.s, h)
                        if err != nil {
                                return nil, err
                        }
                }

                return c, nil
        }
}

func (w *bfsCommitIterator) ForEach(cb func(*Commit) error) error {
        for {
                c, err := w.Next()
                if err == io.EOF {
                        break
                }
                if err != nil {
                        return err
                }

                err = cb(c)
                if err == storer.ErrStop {
                        break
                }
                if err != nil {
                        return err
                }
        }

        return nil
}

func (w *bfsCommitIterator) Close() {}

package object

import (
        "io"

        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/storer"
)

// NewFilterCommitIter returns a CommitIter that walks the commit history,
// starting at the passed commit and visiting its parents in Breadth-first order.
// The commits returned by the CommitIter will validate the passed CommitFilter.
// The history won't be transversed beyond a commit if isLimit is true for it.
// Each commit will be visited only once.
// If the commit history can not be traversed, or the Close() method is called,
// the CommitIter won't return more commits.
// If no isValid is passed, all ancestors of from commit will be valid.
// If no isLimit is limit, all ancestors of all commits will be visited.
func NewFilterCommitIter(
        from *Commit,
        isValid *CommitFilter,
        isLimit *CommitFilter,
) CommitIter {
        var validFilter CommitFilter
        if isValid == nil {
                validFilter = func(_ *Commit) bool {
                        return true
                }
        } else {
                validFilter = *isValid
        }

        var limitFilter CommitFilter
        if isLimit == nil {
                limitFilter = func(_ *Commit) bool {
                        return false
                }
        } else {
                limitFilter = *isLimit
        }

        return &filterCommitIter{
                isValid: validFilter,
                isLimit: limitFilter,
                visited: map[plumbing.Hash]struct{}{},
                queue:   []*Commit{from},
        }
}

// CommitFilter returns a boolean for the passed Commit
type CommitFilter func(*Commit) bool

// filterCommitIter implements CommitIter
type filterCommitIter struct {
        isValid CommitFilter
        isLimit CommitFilter
        visited map[plumbing.Hash]struct{}
        queue   []*Commit
        lastErr error
}

// Next returns the next commit of the CommitIter.
// It will return io.EOF if there are no more commits to visit,
// or an error if the history could not be traversed.
func (w *filterCommitIter) Next() (*Commit, error) {
        var commit *Commit
        var err error
        for {
                commit, err = w.popNewFromQueue()
                if err != nil {
                        return nil, w.close(err)
                }

                w.visited[commit.Hash] = struct{}{}

                if !w.isLimit(commit) {
                        err = w.addToQueue(commit.s, commit.ParentHashes...)
                        if err != nil {
                                return nil, w.close(err)
                        }
                }

                if w.isValid(commit) {
                        return commit, nil
                }
        }
}

// ForEach runs the passed callback over each Commit returned by the CommitIter
// until the callback returns an error or there is no more commits to traverse.
func (w *filterCommitIter) ForEach(cb func(*Commit) error) error {
        for {
                commit, err := w.Next()
                if err == io.EOF {
                        break
                }

                if err != nil {
                        return err
                }

                if err := cb(commit); err == storer.ErrStop {
                        break
                } else if err != nil {
                        return err
                }
        }

        return nil
}

// Error returns the error that caused that the CommitIter is no longer returning commits
func (w *filterCommitIter) Error() error {
        return w.lastErr
}

// Close closes the CommitIter
func (w *filterCommitIter) Close() {
        w.visited = map[plumbing.Hash]struct{}{}
        w.queue = []*Commit{}
        w.isLimit = nil
        w.isValid = nil
}

// close closes the CommitIter with an error
func (w *filterCommitIter) close(err error) error {
        w.Close()
        w.lastErr = err
        return err
}

// popNewFromQueue returns the first new commit from the internal fifo queue,
// or an io.EOF error if the queue is empty
func (w *filterCommitIter) popNewFromQueue() (*Commit, error) {
        var first *Commit
        for {
                if len(w.queue) == 0 {
                        if w.lastErr != nil {
                                return nil, w.lastErr
                        }

                        return nil, io.EOF
                }

                first = w.queue[0]
                w.queue = w.queue[1:]
                if _, ok := w.visited[first.Hash]; ok {
                        continue
                }

                return first, nil
        }
}

// addToQueue adds the passed commits to the internal fifo queue if they weren't seen
// or returns an error if the passed hashes could not be used to get valid commits
func (w *filterCommitIter) addToQueue(
        store storer.EncodedObjectStorer,
        hashes ...plumbing.Hash,
) error {
        for _, hash := range hashes {
                if _, ok := w.visited[hash]; ok {
                        continue
                }

                commit, err := GetCommit(store, hash)
                if err != nil {
                        return err
                }

                w.queue = append(w.queue, commit)
        }

        return nil
}

package object

import (
        "io"

        "github.com/emirpasic/gods/trees/binaryheap"

        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/storer"
)

type commitIteratorByCTime struct {
        seenExternal map[plumbing.Hash]bool
        seen         map[plumbing.Hash]bool
        heap         *binaryheap.Heap
}

// NewCommitIterCTime returns a CommitIter that walks the commit history,
// starting at the given commit and visiting its parents while preserving Committer Time order.
// this appears to be the closest order to `git log`
// The given callback will be called for each visited commit. Each commit will
// be visited only once. If the callback returns an error, walking will stop
// and will return the error. Other errors might be returned if the history
// cannot be traversed (e.g. missing objects). Ignore allows to skip some
// commits from being iterated.
func NewCommitIterCTime(
        c *Commit,
        seenExternal map[plumbing.Hash]bool,
        ignore []plumbing.Hash,
) CommitIter {
        seen := make(map[plumbing.Hash]bool)
        for _, h := range ignore {
                seen[h] = true
        }

        heap := binaryheap.NewWith(func(a, b interface{}) int {
                if a.(*Commit).Committer.When.Before(b.(*Commit).Committer.When) {
                        return 1
                }
                return -1
        })
        heap.Push(c)

        return &commitIteratorByCTime{
                seenExternal: seenExternal,
                seen:         seen,
                heap:         heap,
        }
}

func (w *commitIteratorByCTime) Next() (*Commit, error) {
        var c *Commit
        for {
                cIn, ok := w.heap.Pop()
                if !ok {
                        return nil, io.EOF
                }
                c = cIn.(*Commit)

                if w.seen[c.Hash] || w.seenExternal[c.Hash] {
                        continue
                }

                w.seen[c.Hash] = true

                for _, h := range c.ParentHashes {
                        if w.seen[h] || w.seenExternal[h] {
                                continue
                        }
                        pc, err := GetCommit(c.s, h)
                        if err != nil {
                                return nil, err
                        }
                        w.heap.Push(pc)
                }

                return c, nil
        }
}

func (w *commitIteratorByCTime) ForEach(cb func(*Commit) error) error {
        for {
                c, err := w.Next()
                if err == io.EOF {
                        break
                }
                if err != nil {
                        return err
                }

                err = cb(c)
                if err == storer.ErrStop {
                        break
                }
                if err != nil {
                        return err
                }
        }

        return nil
}

func (w *commitIteratorByCTime) Close() {}

package object

import (
        "io"
        "time"

        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/storer"
)

type commitLimitIter struct {
        sourceIter   CommitIter
        limitOptions LogLimitOptions
}

type LogLimitOptions struct {
        Since    *time.Time
        Until    *time.Time
        TailHash plumbing.Hash
}

func NewCommitLimitIterFromIter(commitIter CommitIter, limitOptions LogLimitOptions) CommitIter {
        iterator := new(commitLimitIter)
        iterator.sourceIter = commitIter
        iterator.limitOptions = limitOptions
        return iterator
}

func (c *commitLimitIter) Next() (*Commit, error) {
        for {
                commit, err := c.sourceIter.Next()
                if err != nil {
                        return nil, err
                }

                if c.limitOptions.Since != nil && commit.Committer.When.Before(*c.limitOptions.Since) {
                        continue
                }
                if c.limitOptions.Until != nil && commit.Committer.When.After(*c.limitOptions.Until) {
                        continue
                }
                if c.limitOptions.TailHash == commit.Hash {
                        return commit, storer.ErrStop
                }
                return commit, nil
        }
}

func (c *commitLimitIter) ForEach(cb func(*Commit) error) error {
        for {
                commit, nextErr := c.Next()
                if nextErr == io.EOF {
                        break
                }
                if nextErr != nil && nextErr != storer.ErrStop {
                        return nextErr
                }
                err := cb(commit)
                if err == storer.ErrStop || nextErr == storer.ErrStop {
                        return nil
                } else if err != nil {
                        return err
                }
        }
        return nil
}

func (c *commitLimitIter) Close() {
        c.sourceIter.Close()
}

package object

import (
        "io"

        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/storer"
)

type commitPathIter struct {
        pathFilter    func(string) bool
        sourceIter    CommitIter
        currentCommit *Commit
        checkParent   bool
}

// NewCommitPathIterFromIter returns a commit iterator which performs diffTree between
// successive trees returned from the commit iterator from the argument. The purpose of this is
// to find the commits that explain how the files that match the path came to be.
// If checkParent is true then the function double checks if potential parent (next commit in a path)
// is one of the parents in the tree (it's used by `git log --all`).
// pathFilter is a function that takes path of file as argument and returns true if we want it
func NewCommitPathIterFromIter(pathFilter func(string) bool, commitIter CommitIter, checkParent bool) CommitIter {
        iterator := new(commitPathIter)
        iterator.sourceIter = commitIter
        iterator.pathFilter = pathFilter
        iterator.checkParent = checkParent
        return iterator
}

// NewCommitFileIterFromIter is kept for compatibility, can be replaced with NewCommitPathIterFromIter
func NewCommitFileIterFromIter(fileName string, commitIter CommitIter, checkParent bool) CommitIter {
        return NewCommitPathIterFromIter(
                func(path string) bool {
                        return path == fileName
                },
                commitIter,
                checkParent,
        )
}

func (c *commitPathIter) Next() (*Commit, error) {
        if c.currentCommit == nil {
                var err error
                c.currentCommit, err = c.sourceIter.Next()
                if err != nil {
                        return nil, err
                }
        }
        commit, commitErr := c.getNextFileCommit()

        // Setting current-commit to nil to prevent unwanted states when errors are raised
        if commitErr != nil {
                c.currentCommit = nil
        }
        return commit, commitErr
}

func (c *commitPathIter) getNextFileCommit() (*Commit, error) {
        var parentTree, currentTree *Tree

        for {
                // Parent-commit can be nil if the current-commit is the initial commit
                parentCommit, parentCommitErr := c.sourceIter.Next()
                if parentCommitErr != nil {
                        // If the parent-commit is beyond the initial commit, keep it nil
                        if parentCommitErr != io.EOF {
                                return nil, parentCommitErr
                        }
                        parentCommit = nil
                }

                if parentTree == nil {
                        var currTreeErr error
                        currentTree, currTreeErr = c.currentCommit.Tree()
                        if currTreeErr != nil {
                                return nil, currTreeErr
                        }
                } else {
                        currentTree = parentTree
                        parentTree = nil
                }

                if parentCommit != nil {
                        var parentTreeErr error
                        parentTree, parentTreeErr = parentCommit.Tree()
                        if parentTreeErr != nil {
                                return nil, parentTreeErr
                        }
                }

                // Find diff between current and parent trees
                changes, diffErr := DiffTree(currentTree, parentTree)
                if diffErr != nil {
                        return nil, diffErr
                }

                found := c.hasFileChange(changes, parentCommit)

                // Storing the current-commit in-case a change is found, and
                // Updating the current-commit for the next-iteration
                prevCommit := c.currentCommit
                c.currentCommit = parentCommit

                if found {
                        return prevCommit, nil
                }

                // If not matches found and if parent-commit is beyond the initial commit, then return with EOF
                if parentCommit == nil {
                        return nil, io.EOF
                }
        }
}

func (c *commitPathIter) hasFileChange(changes Changes, parent *Commit) bool {
        for _, change := range changes {
                if !c.pathFilter(change.name()) {
                        continue
                }

                // filename matches, now check if source iterator contains all commits (from all refs)
                if c.checkParent {
                        // Check if parent is beyond the initial commit
                        if parent == nil || isParentHash(parent.Hash, c.currentCommit) {
                                return true
                        }
                        continue
                }

                return true
        }

        return false
}

func isParentHash(hash plumbing.Hash, commit *Commit) bool {
        for _, h := range commit.ParentHashes {
                if h == hash {
                        return true
                }
        }
        return false
}

func (c *commitPathIter) ForEach(cb func(*Commit) error) error {
        for {
                commit, nextErr := c.Next()
                if nextErr == io.EOF {
                        break
                }
                if nextErr != nil {
                        return nextErr
                }
                err := cb(commit)
                if err == storer.ErrStop {
                        return nil
                } else if err != nil {
                        return err
                }
        }
        return nil
}

func (c *commitPathIter) Close() {
        c.sourceIter.Close()
}

package object

import (
        "bytes"
        "context"

        "github.com/go-git/go-git/v6/utils/merkletrie"
        "github.com/go-git/go-git/v6/utils/merkletrie/noder"
)

// DiffTree compares the content and mode of the blobs found via two
// tree objects.
// DiffTree does not perform rename detection, use DiffTreeWithOptions
// instead to detect renames.
func DiffTree(a, b *Tree) (Changes, error) {
        return DiffTreeContext(context.Background(), a, b)
}

// DiffTreeContext compares the content and mode of the blobs found via two
// tree objects. Provided context must be non-nil.
// An error will be returned if context expires.
func DiffTreeContext(ctx context.Context, a, b *Tree) (Changes, error) {
        return DiffTreeWithOptions(ctx, a, b, nil)
}

// DiffTreeOptions are the configurable options when performing a diff tree.
type DiffTreeOptions struct {
        // DetectRenames is whether the diff tree will use rename detection.
        DetectRenames bool
        // RenameScore is the threshold to of similarity between files to consider
        // that a pair of delete and insert are a rename. The number must be
        // exactly between 0 and 100.
        RenameScore uint
        // RenameLimit is the maximum amount of files that can be compared when
        // detecting renames. The number of comparisons that have to be performed
        // is equal to the number of deleted files * the number of added files.
        // That means, that if 100 files were deleted and 50 files were added, 5000
        // file comparisons may be needed. So, if the rename limit is 50, the number
        // of both deleted and added needs to be equal or less than 50.
        // A value of 0 means no limit.
        RenameLimit uint
        // OnlyExactRenames performs only detection of exact renames and will not perform
        // any detection of renames based on file similarity.
        OnlyExactRenames bool
}

// DefaultDiffTreeOptions are the default and recommended options for the
// diff tree.
var DefaultDiffTreeOptions = &DiffTreeOptions{
        DetectRenames:    true,
        RenameScore:      60,
        RenameLimit:      0,
        OnlyExactRenames: false,
}

// DiffTreeWithOptions compares the content and mode of the blobs found
// via two tree objects with the given options. The provided context
// must be non-nil.
// If no options are passed, no rename detection will be performed. The
// recommended options are DefaultDiffTreeOptions.
// An error will be returned if the context expires.
// This function will be deprecated and removed in v6 so the default
// behaviour of DiffTree is to detect renames.
func DiffTreeWithOptions(
        ctx context.Context,
        a, b *Tree,
        opts *DiffTreeOptions,
) (Changes, error) {
        from := NewTreeRootNode(a)
        to := NewTreeRootNode(b)

        hashEqual := func(a, b noder.Hasher) bool {
                return bytes.Equal(a.Hash(), b.Hash())
        }

        merkletrieChanges, err := merkletrie.DiffTreeContext(ctx, from, to, hashEqual)
        if err != nil {
                if err == merkletrie.ErrCanceled {
                        return nil, ErrCanceled
                }
                return nil, err
        }

        changes, err := newChanges(merkletrieChanges)
        if err != nil {
                return nil, err
        }

        if opts == nil {
                opts = new(DiffTreeOptions)
        }

        if opts.DetectRenames {
                return DetectRenames(changes, opts)
        }

        return changes, nil
}

package object

import (
        "bytes"
        "io"
        "strings"

        "github.com/go-git/go-git/v6/plumbing/filemode"
        "github.com/go-git/go-git/v6/plumbing/storer"
        "github.com/go-git/go-git/v6/utils/binary"
        "github.com/go-git/go-git/v6/utils/ioutil"
)

// File represents git file objects.
type File struct {
        // Name is the path of the file. It might be relative to a tree,
        // depending of the function that generates it.
        Name string
        // Mode is the file mode.
        Mode filemode.FileMode
        // Blob with the contents of the file.
        Blob
}

// NewFile returns a File based on the given blob object
func NewFile(name string, m filemode.FileMode, b *Blob) *File {
        return &File{Name: name, Mode: m, Blob: *b}
}

// Contents returns the contents of a file as a string.
func (f *File) Contents() (content string, err error) {
        reader, err := f.Reader()
        if err != nil {
                return "", err
        }
        defer ioutil.CheckClose(reader, &err)

        buf := new(bytes.Buffer)
        if _, err := buf.ReadFrom(reader); err != nil {
                return "", err
        }

        return buf.String(), nil
}

// IsBinary returns if the file is binary or not
func (f *File) IsBinary() (bin bool, err error) {
        reader, err := f.Reader()
        if err != nil {
                return false, err
        }
        defer ioutil.CheckClose(reader, &err)

        return binary.IsBinary(reader)
}

// Lines returns a slice of lines from the contents of a file, stripping
// all end of line characters. If the last line is empty (does not end
// in an end of line), it is also stripped.
func (f *File) Lines() ([]string, error) {
        content, err := f.Contents()
        if err != nil {
                return nil, err
        }

        splits := strings.Split(content, "\n")
        // remove the last line if it is empty
        if splits[len(splits)-1] == "" {
                return splits[:len(splits)-1], nil
        }

        return splits, nil
}

// FileIter provides an iterator for the files in a tree.
type FileIter struct {
        s storer.EncodedObjectStorer
        w TreeWalker
}

// NewFileIter takes a storer.EncodedObjectStorer and a Tree and returns a
// *FileIter that iterates over all files contained in the tree, recursively.
func NewFileIter(s storer.EncodedObjectStorer, t *Tree) *FileIter {
        return &FileIter{s: s, w: *NewTreeWalker(t, true, nil)}
}

// Next moves the iterator to the next file and returns a pointer to it. If
// there are no more files, it returns io.EOF.
func (iter *FileIter) Next() (*File, error) {
        for {
                name, entry, err := iter.w.Next()
                if err != nil {
                        return nil, err
                }

                if entry.Mode == filemode.Dir || entry.Mode == filemode.Submodule {
                        continue
                }

                blob, err := GetBlob(iter.s, entry.Hash)
                if err != nil {
                        return nil, err
                }

                return NewFile(name, entry.Mode, blob), nil
        }
}

// ForEach call the cb function for each file contained in this iter until
// an error happens or the end of the iter is reached. If plumbing.ErrStop is sent
// the iteration is stop but no error is returned. The iterator is closed.
func (iter *FileIter) ForEach(cb func(*File) error) error {
        defer iter.Close()

        for {
                f, err := iter.Next()
                if err != nil {
                        if err == io.EOF {
                                return nil
                        }

                        return err
                }

                if err := cb(f); err != nil {
                        if err == storer.ErrStop {
                                return nil
                        }

                        return err
                }
        }
}

func (iter *FileIter) Close() {
        iter.w.Close()
}

package object

import (
        "fmt"
        "sort"

        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/storer"
)

// errIsReachable is thrown when first commit is an ancestor of the second
var errIsReachable = fmt.Errorf("first is reachable from second")

// MergeBase mimics the behavior of `git merge-base actual other`, returning the
// best common ancestor between the actual and the passed one.
// The best common ancestors can not be reached from other common ancestors.
func (c *Commit) MergeBase(other *Commit) ([]*Commit, error) {
        // use sortedByCommitDateDesc strategy
        sorted := sortByCommitDateDesc(c, other)
        newer := sorted[0]
        older := sorted[1]

        newerHistory, err := ancestorsIndex(older, newer)
        if err == errIsReachable {
                return []*Commit{older}, nil
        }

        if err != nil {
                return nil, err
        }

        var res []*Commit
        inNewerHistory := isInIndexCommitFilter(newerHistory)
        resIter := NewFilterCommitIter(older, &inNewerHistory, &inNewerHistory)
        _ = resIter.ForEach(func(commit *Commit) error {
                res = append(res, commit)
                return nil
        })

        return Independents(res)
}

// IsAncestor returns true if the actual commit is ancestor of the passed one.
// It returns an error if the history is not transversable
// It mimics the behavior of `git merge --is-ancestor actual other`
func (c *Commit) IsAncestor(other *Commit) (bool, error) {
        found := false
        iter := NewCommitPreorderIter(other, nil, nil)
        err := iter.ForEach(func(comm *Commit) error {
                if comm.Hash != c.Hash {
                        return nil
                }

                found = true
                return storer.ErrStop
        })

        return found, err
}

// ancestorsIndex returns a map with the ancestors of the starting commit if the
// excluded one is not one of them. It returns errIsReachable if the excluded commit
// is ancestor of the starting, or another error if the history is not traversable.
func ancestorsIndex(excluded, starting *Commit) (map[plumbing.Hash]struct{}, error) {
        if excluded.Hash.String() == starting.Hash.String() {
                return nil, errIsReachable
        }

        startingHistory := map[plumbing.Hash]struct{}{}
        startingIter := NewCommitIterBSF(starting, nil, nil)
        err := startingIter.ForEach(func(commit *Commit) error {
                if commit.Hash == excluded.Hash {
                        return errIsReachable
                }

                startingHistory[commit.Hash] = struct{}{}
                return nil
        })

        if err != nil {
                return nil, err
        }

        return startingHistory, nil
}

// Independents returns a subset of the passed commits, that are not reachable the others
// It mimics the behavior of `git merge-base --independent commit...`.
func Independents(commits []*Commit) ([]*Commit, error) {
        // use sortedByCommitDateDesc strategy
        candidates := sortByCommitDateDesc(commits...)
        candidates = removeDuplicated(candidates)

        seen := map[plumbing.Hash]struct{}{}
        var isLimit CommitFilter = func(commit *Commit) bool {
                _, ok := seen[commit.Hash]
                return ok
        }

        if len(candidates) < 2 {
                return candidates, nil
        }

        pos := 0
        for {
                from := candidates[pos]
                others := remove(candidates, from)
                fromHistoryIter := NewFilterCommitIter(from, nil, &isLimit)
                err := fromHistoryIter.ForEach(func(fromAncestor *Commit) error {
                        for _, other := range others {
                                if fromAncestor.Hash == other.Hash {
                                        candidates = remove(candidates, other)
                                        others = remove(others, other)
                                }
                        }

                        if len(candidates) == 1 {
                                return storer.ErrStop
                        }

                        seen[fromAncestor.Hash] = struct{}{}
                        return nil
                })

                if err != nil {
                        return nil, err
                }

                nextPos := indexOf(candidates, from) + 1
                if nextPos >= len(candidates) {
                        break
                }

                pos = nextPos
        }

        return candidates, nil
}

// sortByCommitDateDesc returns the passed commits, sorted by `committer.When desc`
//
// Following this strategy, it is tried to reduce the time needed when walking
// the history from one commit to reach the others. It is assumed that ancestors
// use to be committed before its descendant;
// That way `Independents(A^, A)` will be processed as being `Independents(A, A^)`;
// so starting by `A` it will be reached `A^` way sooner than walking from `A^`
// to the initial commit, and then from `A` to `A^`.
func sortByCommitDateDesc(commits ...*Commit) []*Commit {
        sorted := make([]*Commit, len(commits))
        copy(sorted, commits)
        sort.Slice(sorted, func(i, j int) bool {
                return sorted[i].Committer.When.After(sorted[j].Committer.When)
        })

        return sorted
}

// indexOf returns the first position where target was found in the passed commits
func indexOf(commits []*Commit, target *Commit) int {
        for i, commit := range commits {
                if target.Hash == commit.Hash {
                        return i
                }
        }

        return -1
}

// remove returns the passed commits excluding the commit toDelete
func remove(commits []*Commit, toDelete *Commit) []*Commit {
        res := make([]*Commit, len(commits))
        j := 0
        for _, commit := range commits {
                if commit.Hash == toDelete.Hash {
                        continue
                }

                res[j] = commit
                j++
        }

        return res[:j]
}

// removeDuplicated removes duplicated commits from the passed slice of commits
func removeDuplicated(commits []*Commit) []*Commit {
        seen := make(map[plumbing.Hash]struct{}, len(commits))
        res := make([]*Commit, len(commits))
        j := 0
        for _, commit := range commits {
                if _, ok := seen[commit.Hash]; ok {
                        continue
                }

                seen[commit.Hash] = struct{}{}
                res[j] = commit
                j++
        }

        return res[:j]
}

// isInIndexCommitFilter returns a commitFilter that returns true
// if the commit is in the passed index.
func isInIndexCommitFilter(index map[plumbing.Hash]struct{}) CommitFilter {
        return func(c *Commit) bool {
                _, ok := index[c.Hash]
                return ok
        }
}

// Package object contains implementations of all Git objects and utility
// functions to work with them.
package object

import (
        "bytes"
        "errors"
        "fmt"
        "io"
        "strconv"
        "time"

        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/storer"
)

// ErrUnsupportedObject trigger when a non-supported object is being decoded.
var ErrUnsupportedObject = errors.New("unsupported object type")

// Object is a generic representation of any git object. It is implemented by
// Commit, Tree, Blob, and Tag, and includes the functions that are common to
// them.
//
// Object is returned when an object can be of any type. It is frequently used
// with a type cast to acquire the specific type of object:
//
//        func process(obj Object) {
//                switch o := obj.(type) {
//                case *Commit:
//                        // o is a Commit
//                case *Tree:
//                        // o is a Tree
//                case *Blob:
//                        // o is a Blob
//                case *Tag:
//                        // o is a Tag
//                }
//        }
//
// This interface is intentionally different from plumbing.EncodedObject, which
// is a lower level interface used by storage implementations to read and write
// objects in its encoded form.
type Object interface {
        ID() plumbing.Hash
        Type() plumbing.ObjectType
        Decode(plumbing.EncodedObject) error
        Encode(plumbing.EncodedObject) error
}

// GetObject gets an object from an object storer and decodes it.
func GetObject(s storer.EncodedObjectStorer, h plumbing.Hash) (Object, error) {
        o, err := s.EncodedObject(plumbing.AnyObject, h)
        if err != nil {
                return nil, err
        }

        return DecodeObject(s, o)
}

// DecodeObject decodes an encoded object into an Object and associates it to
// the given object storer.
func DecodeObject(s storer.EncodedObjectStorer, o plumbing.EncodedObject) (Object, error) {
        switch o.Type() {
        case plumbing.CommitObject:
                return DecodeCommit(s, o)
        case plumbing.TreeObject:
                return DecodeTree(s, o)
        case plumbing.BlobObject:
                return DecodeBlob(o)
        case plumbing.TagObject:
                return DecodeTag(s, o)
        default:
                return nil, plumbing.ErrInvalidType
        }
}

// DateFormat is the format being used in the original git implementation
const DateFormat = "Mon Jan 02 15:04:05 2006 -0700"

// Signature is used to identify who and when created a commit or tag.
type Signature struct {
        // Name represents a person name. It is an arbitrary string.
        Name string
        // Email is an email, but it cannot be assumed to be well-formed.
        Email string
        // When is the timestamp of the signature.
        When time.Time
}

// Decode decodes a byte slice into a signature
func (s *Signature) Decode(b []byte) {
        open := bytes.LastIndexByte(b, '<')
        close := bytes.LastIndexByte(b, '>')
        if open == -1 || close == -1 {
                return
        }

        if close < open {
                return
        }

        s.Name = string(bytes.Trim(b[:open], " "))
        s.Email = string(b[open+1 : close])

        hasTime := close+2 < len(b)
        if hasTime {
                s.decodeTimeAndTimeZone(b[close+2:])
        }
}

// Encode encodes a Signature into a writer.
func (s *Signature) Encode(w io.Writer) error {
        if _, err := fmt.Fprintf(w, "%s <%s> ", s.Name, s.Email); err != nil {
                return err
        }
        if err := s.encodeTimeAndTimeZone(w); err != nil {
                return err
        }
        return nil
}

var timeZoneLength = 5

func (s *Signature) decodeTimeAndTimeZone(b []byte) {
        space := bytes.IndexByte(b, ' ')
        if space == -1 {
                space = len(b)
        }

        ts, err := strconv.ParseInt(string(b[:space]), 10, 64)
        if err != nil {
                return
        }

        s.When = time.Unix(ts, 0).In(time.UTC)
        var tzStart = space + 1
        if tzStart >= len(b) || tzStart+timeZoneLength > len(b) {
                return
        }

        timezone := string(b[tzStart : tzStart+timeZoneLength])
        tzhours, err1 := strconv.ParseInt(timezone[0:3], 10, 64)
        tzmins, err2 := strconv.ParseInt(timezone[3:], 10, 64)
        if err1 != nil || err2 != nil {
                return
        }
        if tzhours < 0 {
                tzmins *= -1
        }

        tz := time.FixedZone("", int(tzhours*60*60+tzmins*60))

        s.When = s.When.In(tz)
}

func (s *Signature) encodeTimeAndTimeZone(w io.Writer) error {
        u := s.When.Unix()
        if u < 0 {
                u = 0
        }
        _, err := fmt.Fprintf(w, "%d %s", u, s.When.Format("-0700"))
        return err
}

func (s *Signature) String() string {
        return fmt.Sprintf("%s <%s>", s.Name, s.Email)
}

// ObjectIter provides an iterator for a set of objects.
type ObjectIter struct {
        storer.EncodedObjectIter
        s storer.EncodedObjectStorer
}

// NewObjectIter takes a storer.EncodedObjectStorer and a
// storer.EncodedObjectIter and returns an *ObjectIter that iterates over all
// objects contained in the storer.EncodedObjectIter.
func NewObjectIter(s storer.EncodedObjectStorer, iter storer.EncodedObjectIter) *ObjectIter {
        return &ObjectIter{iter, s}
}

// Next moves the iterator to the next object and returns a pointer to it. If
// there are no more objects, it returns io.EOF.
func (iter *ObjectIter) Next() (Object, error) {
        for {
                obj, err := iter.EncodedObjectIter.Next()
                if err != nil {
                        return nil, err
                }

                o, err := iter.toObject(obj)
                if err == plumbing.ErrInvalidType {
                        continue
                }

                if err != nil {
                        return nil, err
                }

                return o, nil
        }
}

// ForEach call the cb function for each object contained on this iter until
// an error happens or the end of the iter is reached. If ErrStop is sent
// the iteration is stop but no error is returned. The iterator is closed.
func (iter *ObjectIter) ForEach(cb func(Object) error) error {
        return iter.EncodedObjectIter.ForEach(func(obj plumbing.EncodedObject) error {
                o, err := iter.toObject(obj)
                if err == plumbing.ErrInvalidType {
                        return nil
                }

                if err != nil {
                        return err
                }

                return cb(o)
        })
}

func (iter *ObjectIter) toObject(obj plumbing.EncodedObject) (Object, error) {
        switch obj.Type() {
        case plumbing.BlobObject:
                blob := &Blob{}
                return blob, blob.Decode(obj)
        case plumbing.TreeObject:
                tree := &Tree{s: iter.s}
                return tree, tree.Decode(obj)
        case plumbing.CommitObject:
                commit := &Commit{}
                return commit, commit.Decode(obj)
        case plumbing.TagObject:
                tag := &Tag{}
                return tag, tag.Decode(obj)
        default:
                return nil, plumbing.ErrInvalidType
        }
}

package object

import (
        "bytes"
        "context"
        "errors"
        "fmt"
        "io"
        "strconv"
        "strings"

        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/filemode"
        fdiff "github.com/go-git/go-git/v6/plumbing/format/diff"
        "github.com/go-git/go-git/v6/utils/diff"

        dmp "github.com/sergi/go-diff/diffmatchpatch"
)

var (
        ErrCanceled = errors.New("operation canceled")
)

func getPatch(message string, changes ...*Change) (*Patch, error) {
        ctx := context.Background()
        return getPatchContext(ctx, message, changes...)
}

func getPatchContext(ctx context.Context, message string, changes ...*Change) (*Patch, error) {
        var filePatches []fdiff.FilePatch
        for _, c := range changes {
                select {
                case <-ctx.Done():
                        return nil, ErrCanceled
                default:
                }

                fp, err := filePatchWithContext(ctx, c)
                if err != nil {
                        return nil, err
                }

                filePatches = append(filePatches, fp)
        }

        return &Patch{message, filePatches}, nil
}

func filePatchWithContext(ctx context.Context, c *Change) (fdiff.FilePatch, error) {
        from, to, err := c.Files()
        if err != nil {
                return nil, err
        }
        fromContent, fIsBinary, err := fileContent(from)
        if err != nil {
                return nil, err
        }

        toContent, tIsBinary, err := fileContent(to)
        if err != nil {
                return nil, err
        }

        if fIsBinary || tIsBinary {
                return &textFilePatch{from: c.From, to: c.To}, nil
        }

        diffs := diff.Do(fromContent, toContent)

        var chunks []fdiff.Chunk
        for _, d := range diffs {
                select {
                case <-ctx.Done():
                        return nil, ErrCanceled
                default:
                }

                var op fdiff.Operation
                switch d.Type {
                case dmp.DiffEqual:
                        op = fdiff.Equal
                case dmp.DiffDelete:
                        op = fdiff.Delete
                case dmp.DiffInsert:
                        op = fdiff.Add
                }

                chunks = append(chunks, &textChunk{d.Text, op})
        }

        return &textFilePatch{
                chunks: chunks,
                from:   c.From,
                to:     c.To,
        }, nil

}

func fileContent(f *File) (content string, isBinary bool, err error) {
        if f == nil {
                return
        }

        isBinary, err = f.IsBinary()
        if err != nil || isBinary {
                return
        }

        content, err = f.Contents()

        return
}

// Patch is an implementation of fdiff.Patch interface
type Patch struct {
        message     string
        filePatches []fdiff.FilePatch
}

func (p *Patch) FilePatches() []fdiff.FilePatch {
        return p.filePatches
}

func (p *Patch) Message() string {
        return p.message
}

func (p *Patch) Encode(w io.Writer) error {
        ue := fdiff.NewUnifiedEncoder(w, fdiff.DefaultContextLines)

        return ue.Encode(p)
}

func (p *Patch) Stats() FileStats {
        return getFileStatsFromFilePatches(p.FilePatches())
}

func (p *Patch) String() string {
        buf := bytes.NewBuffer(nil)
        err := p.Encode(buf)
        if err != nil {
                return fmt.Sprintf("malformed patch: %s", err.Error())
        }

        return buf.String()
}

// changeEntryWrapper is an implementation of fdiff.File interface
type changeEntryWrapper struct {
        ce ChangeEntry
}

func (f *changeEntryWrapper) Hash() plumbing.Hash {
        if !f.ce.TreeEntry.Mode.IsFile() {
                return plumbing.ZeroHash
        }

        return f.ce.TreeEntry.Hash
}

func (f *changeEntryWrapper) Mode() filemode.FileMode {
        return f.ce.TreeEntry.Mode
}
func (f *changeEntryWrapper) Path() string {
        if !f.ce.TreeEntry.Mode.IsFile() {
                return ""
        }

        return f.ce.Name
}

func (f *changeEntryWrapper) Empty() bool {
        return !f.ce.TreeEntry.Mode.IsFile()
}

// textFilePatch is an implementation of fdiff.FilePatch interface
type textFilePatch struct {
        chunks   []fdiff.Chunk
        from, to ChangeEntry
}

func (tf *textFilePatch) Files() (from fdiff.File, to fdiff.File) {
        f := &changeEntryWrapper{tf.from}
        t := &changeEntryWrapper{tf.to}

        if !f.Empty() {
                from = f
        }

        if !t.Empty() {
                to = t
        }

        return
}

func (tf *textFilePatch) IsBinary() bool {
        return len(tf.chunks) == 0
}

func (tf *textFilePatch) Chunks() []fdiff.Chunk {
        return tf.chunks
}

// textChunk is an implementation of fdiff.Chunk interface
type textChunk struct {
        content string
        op      fdiff.Operation
}

func (t *textChunk) Content() string {
        return t.content
}

func (t *textChunk) Type() fdiff.Operation {
        return t.op
}

// FileStat stores the status of changes in content of a file.
type FileStat struct {
        Name     string
        Addition int
        Deletion int
}

func (fs FileStat) String() string {
        return printStat([]FileStat{fs})
}

// FileStats is a collection of FileStat.
type FileStats []FileStat

func (fileStats FileStats) String() string {
        return printStat(fileStats)
}

// printStat prints the stats of changes in content of files.
// Original implementation: https://github.com/git/git/blob/1a87c842ece327d03d08096395969aca5e0a6996/diff.c#L2615
// Parts of the output:
// <pad><filename><pad>|<pad><changeNumber><pad><+++/---><newline>
// example: " main.go | 10 +++++++--- "
func printStat(fileStats []FileStat) string {
        maxGraphWidth := uint(53)
        maxNameLen := 0
        maxChangeLen := 0

        scaleLinear := func(it, width, max uint) uint {
                if it == 0 || max == 0 {
                        return 0
                }

                return 1 + (it * (width - 1) / max)
        }

        for _, fs := range fileStats {
                if len(fs.Name) > maxNameLen {
                        maxNameLen = len(fs.Name)
                }

                changes := strconv.Itoa(fs.Addition + fs.Deletion)
                if len(changes) > maxChangeLen {
                        maxChangeLen = len(changes)
                }
        }

        result := ""
        for _, fs := range fileStats {
                add := uint(fs.Addition)
                del := uint(fs.Deletion)
                np := maxNameLen - len(fs.Name)
                cp := maxChangeLen - len(strconv.Itoa(fs.Addition+fs.Deletion))

                total := add + del
                if total > maxGraphWidth {
                        add = scaleLinear(add, maxGraphWidth, total)
                        del = scaleLinear(del, maxGraphWidth, total)
                }

                adds := strings.Repeat("+", int(add))
                dels := strings.Repeat("-", int(del))
                namePad := strings.Repeat(" ", np)
                changePad := strings.Repeat(" ", cp)

                result += fmt.Sprintf(" %s%s | %s%d %s%s\n", fs.Name, namePad, changePad, total, adds, dels)
        }
        return result
}

func getFileStatsFromFilePatches(filePatches []fdiff.FilePatch) FileStats {
        var fileStats FileStats

        for _, fp := range filePatches {
                // ignore empty patches (binary files, submodule refs updates)
                if len(fp.Chunks()) == 0 {
                        continue
                }

                cs := FileStat{}
                from, to := fp.Files()
                if from == nil {
                        // New File is created.
                        cs.Name = to.Path()
                } else if to == nil {
                        // File is deleted.
                        cs.Name = from.Path()
                } else if from.Path() != to.Path() {
                        // File is renamed.
                        cs.Name = fmt.Sprintf("%s => %s", from.Path(), to.Path())
                } else {
                        cs.Name = from.Path()
                }

                for _, chunk := range fp.Chunks() {
                        s := chunk.Content()
                        if len(s) == 0 {
                                continue
                        }

                        switch chunk.Type() {
                        case fdiff.Add:
                                cs.Addition += strings.Count(s, "\n")
                                if s[len(s)-1] != '\n' {
                                        cs.Addition++
                                }
                        case fdiff.Delete:
                                cs.Deletion += strings.Count(s, "\n")
                                if s[len(s)-1] != '\n' {
                                        cs.Deletion++
                                }
                        }
                }

                fileStats = append(fileStats, cs)
        }

        return fileStats
}

package object

import (
        "errors"
        "io"
        "sort"
        "strings"

        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/filemode"
        "github.com/go-git/go-git/v6/utils/ioutil"
        "github.com/go-git/go-git/v6/utils/merkletrie"
)

// DetectRenames detects the renames in the given changes on two trees with
// the given options. It will return the given changes grouping additions and
// deletions into modifications when possible.
// If options is nil, the default diff tree options will be used.
func DetectRenames(
        changes Changes,
        opts *DiffTreeOptions,
) (Changes, error) {
        if opts == nil {
                opts = DefaultDiffTreeOptions
        }

        detector := &renameDetector{
                renameScore: int(opts.RenameScore),
                renameLimit: int(opts.RenameLimit),
                onlyExact:   opts.OnlyExactRenames,
        }

        for _, c := range changes {
                action, err := c.Action()
                if err != nil {
                        return nil, err
                }

                switch action {
                case merkletrie.Insert:
                        detector.added = append(detector.added, c)
                case merkletrie.Delete:
                        detector.deleted = append(detector.deleted, c)
                default:
                        detector.modified = append(detector.modified, c)
                }
        }

        return detector.detect()
}

// renameDetector will detect and resolve renames in a set of changes.
// see: https://github.com/eclipse/jgit/blob/master/org.eclipse.jgit/src/org/eclipse/jgit/diff/RenameDetector.java
type renameDetector struct {
        added    []*Change
        deleted  []*Change
        modified []*Change

        renameScore int
        renameLimit int
        onlyExact   bool
}

// detectExactRenames detects matches files that were deleted with files that
// were added where the hash is the same on both. If there are multiple targets
// the one with the most similar path will be chosen as the rename and the
// rest as either deletions or additions.
func (d *renameDetector) detectExactRenames() {
        added := groupChangesByHash(d.added)
        deletes := groupChangesByHash(d.deleted)
        var uniqueAdds []*Change
        var nonUniqueAdds [][]*Change
        var addedLeft []*Change

        for _, cs := range added {
                if len(cs) == 1 {
                        uniqueAdds = append(uniqueAdds, cs[0])
                } else {
                        nonUniqueAdds = append(nonUniqueAdds, cs)
                }
        }

        for _, c := range uniqueAdds {
                hash := changeHash(c)
                deleted := deletes[hash]

                if len(deleted) == 1 {
                        if sameMode(c, deleted[0]) {
                                d.modified = append(d.modified, &Change{From: deleted[0].From, To: c.To})
                                delete(deletes, hash)
                        } else {
                                addedLeft = append(addedLeft, c)
                        }
                } else if len(deleted) > 1 {
                        bestMatch := bestNameMatch(c, deleted)
                        if bestMatch != nil && sameMode(c, bestMatch) {
                                d.modified = append(d.modified, &Change{From: bestMatch.From, To: c.To})
                                delete(deletes, hash)

                                var newDeletes = make([]*Change, 0, len(deleted)-1)
                                for _, d := range deleted {
                                        if d != bestMatch {
                                                newDeletes = append(newDeletes, d)
                                        }
                                }
                                deletes[hash] = newDeletes
                        }
                } else {
                        addedLeft = append(addedLeft, c)
                }
        }

        for _, added := range nonUniqueAdds {
                hash := changeHash(added[0])
                deleted := deletes[hash]

                if len(deleted) == 1 {
                        deleted := deleted[0]
                        bestMatch := bestNameMatch(deleted, added)
                        if bestMatch != nil && sameMode(deleted, bestMatch) {
                                d.modified = append(d.modified, &Change{From: deleted.From, To: bestMatch.To})
                                delete(deletes, hash)

                                for _, c := range added {
                                        if c != bestMatch {
                                                addedLeft = append(addedLeft, c)
                                        }
                                }
                        } else {
                                addedLeft = append(addedLeft, added...)
                        }
                } else if len(deleted) > 1 {
                        maxSize := len(deleted) * len(added)
                        if d.renameLimit > 0 && d.renameLimit < maxSize {
                                maxSize = d.renameLimit
                        }

                        matrix := make(similarityMatrix, 0, maxSize)

                        for delIdx, del := range deleted {
                                deletedName := changeName(del)

                                for addIdx, add := range added {
                                        addedName := changeName(add)

                                        score := nameSimilarityScore(addedName, deletedName)
                                        matrix = append(matrix, similarityPair{added: addIdx, deleted: delIdx, score: score})

                                        if len(matrix) >= maxSize {
                                                break
                                        }
                                }

                                if len(matrix) >= maxSize {
                                        break
                                }
                        }

                        sort.Stable(matrix)

                        usedAdds := make(map[*Change]struct{})
                        usedDeletes := make(map[*Change]struct{})
                        for i := len(matrix) - 1; i >= 0; i-- {
                                del := deleted[matrix[i].deleted]
                                add := added[matrix[i].added]

                                if add == nil || del == nil {
                                        // it was already matched
                                        continue
                                }

                                usedAdds[add] = struct{}{}
                                usedDeletes[del] = struct{}{}
                                d.modified = append(d.modified, &Change{From: del.From, To: add.To})
                                added[matrix[i].added] = nil
                                deleted[matrix[i].deleted] = nil
                        }

                        for _, c := range added {
                                if _, ok := usedAdds[c]; !ok && c != nil {
                                        addedLeft = append(addedLeft, c)
                                }
                        }

                        var newDeletes = make([]*Change, 0, len(deleted)-len(usedDeletes))
                        for _, c := range deleted {
                                if _, ok := usedDeletes[c]; !ok && c != nil {
                                        newDeletes = append(newDeletes, c)
                                }
                        }
                        deletes[hash] = newDeletes
                } else {
                        addedLeft = append(addedLeft, added...)
                }
        }

        d.added = addedLeft
        d.deleted = nil
        for _, dels := range deletes {
                d.deleted = append(d.deleted, dels...)
        }
}

// detectContentRenames detects renames based on the similarity of the content
// in the files by building a matrix of pairs between sources and destinations
// and matching by the highest score.
// see: https://github.com/eclipse/jgit/blob/master/org.eclipse.jgit/src/org/eclipse/jgit/diff/SimilarityRenameDetector.java
func (d *renameDetector) detectContentRenames() error {
        cnt := max(len(d.added), len(d.deleted))
        if d.renameLimit > 0 && cnt > d.renameLimit {
                return nil
        }

        srcs, dsts := d.deleted, d.added
        matrix, err := buildSimilarityMatrix(srcs, dsts, d.renameScore)
        if err != nil {
                return err
        }
        renames := make([]*Change, 0, min(len(matrix), len(dsts)))

        // Match rename pairs on a first come, first serve basis until
        // we have looked at everything that is above the minimum score.
        for i := len(matrix) - 1; i >= 0; i-- {
                pair := matrix[i]
                src := srcs[pair.deleted]
                dst := dsts[pair.added]

                if dst == nil || src == nil {
                        // It was already matched before
                        continue
                }

                renames = append(renames, &Change{From: src.From, To: dst.To})

                // Claim destination and source as matched
                dsts[pair.added] = nil
                srcs[pair.deleted] = nil
        }

        d.modified = append(d.modified, renames...)
        d.added = compactChanges(dsts)
        d.deleted = compactChanges(srcs)

        return nil
}

func (d *renameDetector) detect() (Changes, error) {
        if len(d.added) > 0 && len(d.deleted) > 0 {
                d.detectExactRenames()

                if !d.onlyExact {
                        if err := d.detectContentRenames(); err != nil {
                                return nil, err
                        }
                }
        }

        result := make(Changes, 0, len(d.added)+len(d.deleted)+len(d.modified))
        result = append(result, d.added...)
        result = append(result, d.deleted...)
        result = append(result, d.modified...)

        sort.Stable(result)

        return result, nil
}

func bestNameMatch(change *Change, changes []*Change) *Change {
        var best *Change
        var bestScore int

        cname := changeName(change)

        for _, c := range changes {
                score := nameSimilarityScore(cname, changeName(c))
                if score > bestScore {
                        bestScore = score
                        best = c
                }
        }

        return best
}

func nameSimilarityScore(a, b string) int {
        aDirLen := strings.LastIndexByte(a, '/') + 1
        bDirLen := strings.LastIndexByte(b, '/') + 1

        dirMin := min(aDirLen, bDirLen)
        dirMax := max(aDirLen, bDirLen)

        var dirScoreLtr, dirScoreRtl int
        if dirMax == 0 {
                dirScoreLtr = 100
                dirScoreRtl = 100
        } else {
                var dirSim int

                for ; dirSim < dirMin; dirSim++ {
                        if a[dirSim] != b[dirSim] {
                                break
                        }
                }

                dirScoreLtr = dirSim * 100 / dirMax

                if dirScoreLtr == 100 {
                        dirScoreRtl = 100
                } else {
                        for dirSim = 0; dirSim < dirMin; dirSim++ {
                                if a[aDirLen-1-dirSim] != b[bDirLen-1-dirSim] {
                                        break
                                }
                        }
                        dirScoreRtl = dirSim * 100 / dirMax
                }
        }

        fileMin := min(len(a)-aDirLen, len(b)-bDirLen)
        fileMax := max(len(a)-aDirLen, len(b)-bDirLen)

        fileSim := 0
        for ; fileSim < fileMin; fileSim++ {
                if a[len(a)-1-fileSim] != b[len(b)-1-fileSim] {
                        break
                }
        }
        fileScore := fileSim * 100 / fileMax

        return (((dirScoreLtr + dirScoreRtl) * 25) + (fileScore * 50)) / 100
}

func changeName(c *Change) string {
        if c.To != empty {
                return c.To.Name
        }
        return c.From.Name
}

func changeHash(c *Change) plumbing.Hash {
        if c.To != empty {
                return c.To.TreeEntry.Hash
        }

        return c.From.TreeEntry.Hash
}

func changeMode(c *Change) filemode.FileMode {
        if c.To != empty {
                return c.To.TreeEntry.Mode
        }

        return c.From.TreeEntry.Mode
}

func sameMode(a, b *Change) bool {
        return changeMode(a) == changeMode(b)
}

func groupChangesByHash(changes []*Change) map[plumbing.Hash][]*Change {
        var result = make(map[plumbing.Hash][]*Change)
        for _, c := range changes {
                hash := changeHash(c)
                result[hash] = append(result[hash], c)
        }
        return result
}

type similarityMatrix []similarityPair

func (m similarityMatrix) Len() int      { return len(m) }
func (m similarityMatrix) Swap(i, j int) { m[i], m[j] = m[j], m[i] }
func (m similarityMatrix) Less(i, j int) bool {
        if m[i].score == m[j].score {
                if m[i].added == m[j].added {
                        return m[i].deleted < m[j].deleted
                }
                return m[i].added < m[j].added
        }
        return m[i].score < m[j].score
}

type similarityPair struct {
        // index of the added file
        added int
        // index of the deleted file
        deleted int
        // similarity score
        score int
}

func max(a, b int) int {
        if a > b {
                return a
        }
        return b
}

func min(a, b int) int {
        if a < b {
                return a
        }
        return b
}

const maxMatrixSize = 10000

func buildSimilarityMatrix(srcs, dsts []*Change, renameScore int) (similarityMatrix, error) {
        // Allocate for the worst-case scenario where every pair has a score
        // that we need to consider. We might not need that many.
        matrixSize := len(srcs) * len(dsts)
        if matrixSize > maxMatrixSize {
                matrixSize = maxMatrixSize
        }
        matrix := make(similarityMatrix, 0, matrixSize)
        srcSizes := make([]int64, len(srcs))
        dstSizes := make([]int64, len(dsts))
        dstTooLarge := make(map[int]bool)

        // Consider each pair of files, if the score is above the minimum
        // threshold we need to record that scoring in the matrix so we can
        // later find the best matches.
outerLoop:
        for srcIdx, src := range srcs {
                if changeMode(src) != filemode.Regular {
                        continue
                }

                // Declare the from file and the similarity index here to be able to
                // reuse it inside the inner loop. The reason to not initialize them
                // here is so we can skip the initialization in case they happen to
                // not be needed later. They will be initialized inside the inner
                // loop if and only if they're needed and reused in subsequent passes.
                var from *File
                var s *similarityIndex
                var err error
                for dstIdx, dst := range dsts {
                        if changeMode(dst) != filemode.Regular {
                                continue
                        }

                        if dstTooLarge[dstIdx] {
                                continue
                        }

                        var to *File
                        srcSize := srcSizes[srcIdx]
                        if srcSize == 0 {
                                from, _, err = src.Files()
                                if err != nil {
                                        return nil, err
                                }
                                srcSize = from.Size + 1
                                srcSizes[srcIdx] = srcSize
                        }

                        dstSize := dstSizes[dstIdx]
                        if dstSize == 0 {
                                _, to, err = dst.Files()
                                if err != nil {
                                        return nil, err
                                }
                                dstSize = to.Size + 1
                                dstSizes[dstIdx] = dstSize
                        }

                        min, max := srcSize, dstSize
                        if dstSize < srcSize {
                                min = dstSize
                                max = srcSize
                        }

                        if int(min*100/max) < renameScore {
                                // File sizes are too different to be a match
                                continue
                        }

                        if s == nil {
                                s, err = fileSimilarityIndex(from)
                                if err != nil {
                                        if err == errIndexFull {
                                                continue outerLoop
                                        }
                                        return nil, err
                                }
                        }

                        if to == nil {
                                _, to, err = dst.Files()
                                if err != nil {
                                        return nil, err
                                }
                        }

                        di, err := fileSimilarityIndex(to)
                        if err != nil {
                                if err == errIndexFull {
                                        dstTooLarge[dstIdx] = true
                                }

                                return nil, err
                        }

                        contentScore := s.score(di, 10000)
                        // The name score returns a value between 0 and 100, so we need to
                        // convert it to the same range as the content score.
                        nameScore := nameSimilarityScore(src.From.Name, dst.To.Name) * 100
                        score := (contentScore*99 + nameScore*1) / 10000

                        if score < renameScore {
                                continue
                        }

                        matrix = append(matrix, similarityPair{added: dstIdx, deleted: srcIdx, score: score})
                }
        }

        sort.Stable(matrix)

        return matrix, nil
}

func compactChanges(changes []*Change) []*Change {
        var result []*Change
        for _, c := range changes {
                if c != nil {
                        result = append(result, c)
                }
        }
        return result
}

const (
        keyShift      = 32
        maxCountValue = (1 << keyShift) - 1
)

var errIndexFull = errors.New("index is full")

// similarityIndex is an index structure of lines/blocks in one file.
// This structure can be used to compute an approximation of the similarity
// between two files.
// To save space in memory, this index uses a space efficient encoding which
// will not exceed 1MiB per instance. The index starts out at a smaller size
// (closer to 2KiB), but may grow as more distinct blocks within the scanned
// file are discovered.
// see: https://github.com/eclipse/jgit/blob/master/org.eclipse.jgit/src/org/eclipse/jgit/diff/SimilarityIndex.java
type similarityIndex struct {
        hashed uint64
        // number of non-zero entries in hashes
        numHashes int
        growAt    int
        hashes    []keyCountPair
        hashBits  int
}

func fileSimilarityIndex(f *File) (*similarityIndex, error) {
        idx := newSimilarityIndex()
        if err := idx.hash(f); err != nil {
                return nil, err
        }

        sort.Stable(keyCountPairs(idx.hashes))

        return idx, nil
}

func newSimilarityIndex() *similarityIndex {
        return &similarityIndex{
                hashBits: 8,
                hashes:   make([]keyCountPair, 1<<8),
                growAt:   shouldGrowAt(8),
        }
}

func (i *similarityIndex) hash(f *File) error {
        isBin, err := f.IsBinary()
        if err != nil {
                return err
        }

        r, err := f.Reader()
        if err != nil {
                return err
        }

        defer ioutil.CheckClose(r, &err)

        return i.hashContent(r, f.Size, isBin)
}

func (i *similarityIndex) hashContent(r io.Reader, size int64, isBin bool) error {
        var buf = make([]byte, 4096)
        var ptr, cnt int
        remaining := size

        for 0 < remaining {
                hash := 5381
                var blockHashedCnt uint64

                // Hash one line or block, whatever happens first
                n := int64(0)
                for {
                        if ptr == cnt {
                                ptr = 0
                                var err error
                                cnt, err = io.ReadFull(r, buf)
                                if err != nil && err != io.ErrUnexpectedEOF {
                                        return err
                                }

                                if cnt == 0 {
                                        return io.EOF
                                }
                        }
                        n++
                        c := buf[ptr] & 0xff
                        ptr++

                        // Ignore CR in CRLF sequence if it's text
                        if !isBin && c == '\r' && ptr < cnt && buf[ptr] == '\n' {
                                continue
                        }
                        blockHashedCnt++

                        if c == '\n' {
                                break
                        }

                        hash = (hash << 5) + hash + int(c)

                        if n >= 64 || n >= remaining {
                                break
                        }
                }
                i.hashed += blockHashedCnt
                if err := i.add(hash, blockHashedCnt); err != nil {
                        return err
                }
                remaining -= n
        }

        return nil
}

// score computes the similarity score between this index and another one.
// A region of a file is defined as a line in a text file or a fixed-size
// block in a binary file. To prepare an index, each region in the file is
// hashed; the values and counts of hashes are retained in a sorted table.
// Define the similarity fraction F as the count of matching regions between
// the two files divided between the maximum count of regions in either file.
// The similarity score is F multiplied by the maxScore constant, yielding a
// range [0, maxScore]. It is defined as maxScore for the degenerate case of
// two empty files.
// The similarity score is symmetrical; i.e. a.score(b) == b.score(a).
func (i *similarityIndex) score(other *similarityIndex, maxScore int) int {
        var maxHashed = i.hashed
        if maxHashed < other.hashed {
                maxHashed = other.hashed
        }
        if maxHashed == 0 {
                return maxScore
        }

        return int(i.common(other) * uint64(maxScore) / maxHashed)
}

func (i *similarityIndex) common(dst *similarityIndex) uint64 {
        srcIdx, dstIdx := 0, 0
        if i.numHashes == 0 || dst.numHashes == 0 {
                return 0
        }

        var common uint64
        srcKey, dstKey := i.hashes[srcIdx].key(), dst.hashes[dstIdx].key()

        for {
                if srcKey == dstKey {
                        srcCnt, dstCnt := i.hashes[srcIdx].count(), dst.hashes[dstIdx].count()
                        if srcCnt < dstCnt {
                                common += srcCnt
                        } else {
                                common += dstCnt
                        }

                        srcIdx++
                        if srcIdx == len(i.hashes) {
                                break
                        }
                        srcKey = i.hashes[srcIdx].key()

                        dstIdx++
                        if dstIdx == len(dst.hashes) {
                                break
                        }
                        dstKey = dst.hashes[dstIdx].key()
                } else if srcKey < dstKey {
                        // Region of src that is not in dst
                        srcIdx++
                        if srcIdx == len(i.hashes) {
                                break
                        }
                        srcKey = i.hashes[srcIdx].key()
                } else {
                        // Region of dst that is not in src
                        dstIdx++
                        if dstIdx == len(dst.hashes) {
                                break
                        }
                        dstKey = dst.hashes[dstIdx].key()
                }
        }

        return common
}

func (i *similarityIndex) add(key int, cnt uint64) error {
        key = int(uint32(key) * 0x9e370001 >> 1)

        j := i.slot(key)
        for {
                v := i.hashes[j]
                if v == 0 {
                        // It's an empty slot, so we can store it here.
                        if i.growAt <= i.numHashes {
                                if err := i.grow(); err != nil {
                                        return err
                                }
                                j = i.slot(key)
                                continue
                        }

                        var err error
                        i.hashes[j], err = newKeyCountPair(key, cnt)
                        if err != nil {
                                return err
                        }
                        i.numHashes++
                        return nil
                } else if v.key() == key {
                        // It's the same key, so increment the counter.
                        var err error
                        i.hashes[j], err = newKeyCountPair(key, v.count()+cnt)
                        return err
                } else if j+1 >= len(i.hashes) {
                        j = 0
                } else {
                        j++
                }
        }
}

type keyCountPair uint64

func newKeyCountPair(key int, cnt uint64) (keyCountPair, error) {
        if cnt > maxCountValue {
                return 0, errIndexFull
        }

        return keyCountPair((uint64(key) << keyShift) | cnt), nil
}

func (p keyCountPair) key() int {
        return int(p >> keyShift)
}

func (p keyCountPair) count() uint64 {
        return uint64(p) & maxCountValue
}

func (i *similarityIndex) slot(key int) int {
        // We use 31 - hashBits because the upper bit was already forced
        // to be 0 and we want the remaining high bits to be used as the
        // table slot.
        return int(uint32(key) >> uint(31-i.hashBits))
}

func shouldGrowAt(hashBits int) int {
        return (1 << uint(hashBits)) * (hashBits - 3) / hashBits
}

func (i *similarityIndex) grow() error {
        if i.hashBits == 30 {
                return errIndexFull
        }

        old := i.hashes

        i.hashBits++
        i.growAt = shouldGrowAt(i.hashBits)

        // TODO(erizocosmico): find a way to check if it will OOM and return
        // errIndexFull instead.
        i.hashes = make([]keyCountPair, 1<<uint(i.hashBits))

        for _, v := range old {
                if v != 0 {
                        j := i.slot(v.key())
                        for i.hashes[j] != 0 {
                                j++
                                if j >= len(i.hashes) {
                                        j = 0
                                }
                        }
                        i.hashes[j] = v
                }
        }

        return nil
}

type keyCountPairs []keyCountPair

func (p keyCountPairs) Len() int           { return len(p) }
func (p keyCountPairs) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }
func (p keyCountPairs) Less(i, j int) bool { return p[i] < p[j] }

package object

import "bytes"

const (
        signatureTypeUnknown signatureType = iota
        signatureTypeOpenPGP
        signatureTypeX509
        signatureTypeSSH
)

var (
        // openPGPSignatureFormat is the format of an OpenPGP signature.
        openPGPSignatureFormat = signatureFormat{
                []byte("-----BEGIN PGP SIGNATURE-----"),
                []byte("-----BEGIN PGP MESSAGE-----"),
        }
        // x509SignatureFormat is the format of an X509 signature, which is
        // a PKCS#7 (S/MIME) signature.
        x509SignatureFormat = signatureFormat{
                []byte("-----BEGIN CERTIFICATE-----"),
                []byte("-----BEGIN SIGNED MESSAGE-----"),
        }

        // sshSignatureFormat is the format of an SSH signature.
        sshSignatureFormat = signatureFormat{
                []byte("-----BEGIN SSH SIGNATURE-----"),
        }
)

var (
        // knownSignatureFormats is a map of known signature formats, indexed by
        // their signatureType.
        knownSignatureFormats = map[signatureType]signatureFormat{
                signatureTypeOpenPGP: openPGPSignatureFormat,
                signatureTypeX509:    x509SignatureFormat,
                signatureTypeSSH:     sshSignatureFormat,
        }
)

// signatureType represents the type of the signature.
type signatureType int8

// signatureFormat represents the beginning of a signature.
type signatureFormat [][]byte

// typeForSignature returns the type of the signature based on its format.
func typeForSignature(b []byte) signatureType {
        for t, i := range knownSignatureFormats {
                for _, begin := range i {
                        if bytes.HasPrefix(b, begin) {
                                return t
                        }
                }
        }
        return signatureTypeUnknown
}

// parseSignedBytes returns the position of the last signature block found in
// the given bytes. If no signature block is found, it returns -1.
//
// When multiple signature blocks are found, the position of the last one is
// returned. Any tailing bytes after this signature block start should be
// considered part of the signature.
//
// Given this, it would be safe to use the returned position to split the bytes
// into two parts: the first part containing the message, the second part
// containing the signature.
//
// Example:
//
//        message := []byte(`Message with signature
//
//        -----BEGIN SSH SIGNATURE-----
//        ...`)
//
//        var signature string
//        if pos, _ := parseSignedBytes(message); pos != -1 {
//                signature = string(message[pos:])
//                message = message[:pos]
//        }
//
// This logic is on par with git's gpg-interface.c:parse_signed_buffer().
// https://github.com/git/git/blob/7c2ef319c52c4997256f5807564523dfd4acdfc7/gpg-interface.c#L668
func parseSignedBytes(b []byte) (int, signatureType) {
        var n, match = 0, -1
        var t signatureType
        for n < len(b) {
                var i = b[n:]
                if st := typeForSignature(i); st != signatureTypeUnknown {
                        match = n
                        t = st
                }
                if eol := bytes.IndexByte(i, '\n'); eol >= 0 {
                        n += eol + 1
                        continue
                }
                // If we reach this point, we've reached the end.
                break
        }
        return match, t
}

package object

import (
        "bytes"
        "fmt"
        "io"
        "strings"

        "github.com/ProtonMail/go-crypto/openpgp"
        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/storer"
        "github.com/go-git/go-git/v6/utils/ioutil"
        "github.com/go-git/go-git/v6/utils/sync"
)

// Tag represents an annotated tag object. It points to a single git object of
// any type, but tags typically are applied to commit or blob objects. It
// provides a reference that associates the target with a tag name. It also
// contains meta-information about the tag, including the tagger, tag date and
// message.
//
// Note that this is not used for lightweight tags.
//
// https://git-scm.com/book/en/v2/Git-Internals-Git-References#Tags
type Tag struct {
        // Hash of the tag.
        Hash plumbing.Hash
        // Name of the tag.
        Name string
        // Tagger is the one who created the tag.
        Tagger Signature
        // Message is an arbitrary text message.
        Message string
        // PGPSignature is the PGP signature of the tag.
        PGPSignature string
        // TargetType is the object type of the target.
        TargetType plumbing.ObjectType
        // Target is the hash of the target object.
        Target plumbing.Hash

        s storer.EncodedObjectStorer
}

// GetTag gets a tag from an object storer and decodes it.
func GetTag(s storer.EncodedObjectStorer, h plumbing.Hash) (*Tag, error) {
        o, err := s.EncodedObject(plumbing.TagObject, h)
        if err != nil {
                return nil, err
        }

        return DecodeTag(s, o)
}

// DecodeTag decodes an encoded object into a *Commit and associates it to the
// given object storer.
func DecodeTag(s storer.EncodedObjectStorer, o plumbing.EncodedObject) (*Tag, error) {
        t := &Tag{s: s}
        if err := t.Decode(o); err != nil {
                return nil, err
        }

        return t, nil
}

// ID returns the object ID of the tag, not the object that the tag references.
// The returned value will always match the current value of Tag.Hash.
//
// ID is present to fulfill the Object interface.
func (t *Tag) ID() plumbing.Hash {
        return t.Hash
}

// Type returns the type of object. It always returns plumbing.TagObject.
//
// Type is present to fulfill the Object interface.
func (t *Tag) Type() plumbing.ObjectType {
        return plumbing.TagObject
}

// Decode transforms a plumbing.EncodedObject into a Tag struct.
func (t *Tag) Decode(o plumbing.EncodedObject) (err error) {
        if o.Type() != plumbing.TagObject {
                return ErrUnsupportedObject
        }

        t.Hash = o.Hash()

        reader, err := o.Reader()
        if err != nil {
                return err
        }
        defer ioutil.CheckClose(reader, &err)

        r := sync.GetBufioReader(reader)
        defer sync.PutBufioReader(r)

        for {
                var line []byte
                line, err = r.ReadBytes('\n')
                if err != nil && err != io.EOF {
                        return err
                }

                line = bytes.TrimSpace(line)
                if len(line) == 0 {
                        break // Start of message
                }

                split := bytes.SplitN(line, []byte{' '}, 2)
                switch string(split[0]) {
                case "object":
                        t.Target = plumbing.NewHash(string(split[1]))
                case "type":
                        t.TargetType, err = plumbing.ParseObjectType(string(split[1]))
                        if err != nil {
                                return err
                        }
                case "tag":
                        t.Name = string(split[1])
                case "tagger":
                        t.Tagger.Decode(split[1])
                }

                if err == io.EOF {
                        return nil
                }
        }

        data, err := io.ReadAll(r)
        if err != nil {
                return err
        }
        if sm, _ := parseSignedBytes(data); sm >= 0 {
                t.PGPSignature = string(data[sm:])
                data = data[:sm]
        }
        t.Message = string(data)

        return nil
}

// Encode transforms a Tag into a plumbing.EncodedObject.
func (t *Tag) Encode(o plumbing.EncodedObject) error {
        return t.encode(o, true)
}

// EncodeWithoutSignature export a Tag into a plumbing.EncodedObject without the signature (correspond to the payload of the PGP signature).
func (t *Tag) EncodeWithoutSignature(o plumbing.EncodedObject) error {
        return t.encode(o, false)
}

func (t *Tag) encode(o plumbing.EncodedObject, includeSig bool) (err error) {
        o.SetType(plumbing.TagObject)
        w, err := o.Writer()
        if err != nil {
                return err
        }
        defer ioutil.CheckClose(w, &err)

        if _, err = fmt.Fprintf(w,
                "object %s\ntype %s\ntag %s\ntagger ",
                t.Target.String(), t.TargetType.Bytes(), t.Name); err != nil {
                return err
        }

        if err = t.Tagger.Encode(w); err != nil {
                return err
        }

        if _, err = fmt.Fprint(w, "\n\n"); err != nil {
                return err
        }

        if _, err = fmt.Fprint(w, t.Message); err != nil {
                return err
        }

        // Note that this is highly sensitive to what it sent along in the message.
        // Message *always* needs to end with a newline, or else the message and the
        // signature will be concatenated into a corrupt object. Since this is a
        // lower-level method, we assume you know what you are doing and have already
        // done the needful on the message in the caller.
        if includeSig {
                if _, err = fmt.Fprint(w, t.PGPSignature); err != nil {
                        return err
                }
        }

        return err
}

// Commit returns the commit pointed to by the tag. If the tag points to a
// different type of object ErrUnsupportedObject will be returned.
func (t *Tag) Commit() (*Commit, error) {
        if t.TargetType != plumbing.CommitObject {
                return nil, ErrUnsupportedObject
        }

        o, err := t.s.EncodedObject(plumbing.CommitObject, t.Target)
        if err != nil {
                return nil, err
        }

        return DecodeCommit(t.s, o)
}

// Tree returns the tree pointed to by the tag. If the tag points to a commit
// object the tree of that commit will be returned. If the tag does not point
// to a commit or tree object ErrUnsupportedObject will be returned.
func (t *Tag) Tree() (*Tree, error) {
        switch t.TargetType {
        case plumbing.CommitObject:
                c, err := t.Commit()
                if err != nil {
                        return nil, err
                }

                return c.Tree()
        case plumbing.TreeObject:
                return GetTree(t.s, t.Target)
        default:
                return nil, ErrUnsupportedObject
        }
}

// Blob returns the blob pointed to by the tag. If the tag points to a
// different type of object ErrUnsupportedObject will be returned.
func (t *Tag) Blob() (*Blob, error) {
        if t.TargetType != plumbing.BlobObject {
                return nil, ErrUnsupportedObject
        }

        return GetBlob(t.s, t.Target)
}

// Object returns the object pointed to by the tag.
func (t *Tag) Object() (Object, error) {
        o, err := t.s.EncodedObject(t.TargetType, t.Target)
        if err != nil {
                return nil, err
        }

        return DecodeObject(t.s, o)
}

// String returns the meta information contained in the tag as a formatted
// string.
func (t *Tag) String() string {
        obj, _ := t.Object()

        return fmt.Sprintf(
                "%s %s\nTagger: %s\nDate:   %s\n\n%s\n%s",
                plumbing.TagObject, t.Name, t.Tagger.String(), t.Tagger.When.Format(DateFormat),
                t.Message, objectAsString(obj),
        )
}

// Verify performs PGP verification of the tag with a provided armored
// keyring and returns openpgp.Entity associated with verifying key on success.
func (t *Tag) Verify(armoredKeyRing string) (*openpgp.Entity, error) {
        keyRingReader := strings.NewReader(armoredKeyRing)
        keyring, err := openpgp.ReadArmoredKeyRing(keyRingReader)
        if err != nil {
                return nil, err
        }

        // Extract signature.
        signature := strings.NewReader(t.PGPSignature)

        encoded := &plumbing.MemoryObject{}
        // Encode tag components, excluding signature and get a reader object.
        if err := t.EncodeWithoutSignature(encoded); err != nil {
                return nil, err
        }
        er, err := encoded.Reader()
        if err != nil {
                return nil, err
        }

        return openpgp.CheckArmoredDetachedSignature(keyring, er, signature, nil)
}

// TagIter provides an iterator for a set of tags.
type TagIter struct {
        storer.EncodedObjectIter
        s storer.EncodedObjectStorer
}

// NewTagIter takes a storer.EncodedObjectStorer and a
// storer.EncodedObjectIter and returns a *TagIter that iterates over all
// tags contained in the storer.EncodedObjectIter.
//
// Any non-tag object returned by the storer.EncodedObjectIter is skipped.
func NewTagIter(s storer.EncodedObjectStorer, iter storer.EncodedObjectIter) *TagIter {
        return &TagIter{iter, s}
}

// Next moves the iterator to the next tag and returns a pointer to it. If
// there are no more tags, it returns io.EOF.
func (iter *TagIter) Next() (*Tag, error) {
        obj, err := iter.EncodedObjectIter.Next()
        if err != nil {
                return nil, err
        }

        return DecodeTag(iter.s, obj)
}

// ForEach call the cb function for each tag contained on this iter until
// an error happens or the end of the iter is reached. If ErrStop is sent
// the iteration is stop but no error is returned. The iterator is closed.
func (iter *TagIter) ForEach(cb func(*Tag) error) error {
        return iter.EncodedObjectIter.ForEach(func(obj plumbing.EncodedObject) error {
                t, err := DecodeTag(iter.s, obj)
                if err != nil {
                        return err
                }

                return cb(t)
        })
}

func objectAsString(obj Object) string {
        switch o := obj.(type) {
        case *Commit:
                return o.String()
        default:
                return ""
        }
}

package object

import (
        "context"
        "errors"
        "fmt"
        "io"
        "path"
        "path/filepath"
        "sort"
        "strings"

        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/filemode"
        "github.com/go-git/go-git/v6/plumbing/storer"
        "github.com/go-git/go-git/v6/utils/ioutil"
        "github.com/go-git/go-git/v6/utils/sync"
)

const (
        maxTreeDepth      = 1024
        startingStackSize = 8
)

// New errors defined by this package.
var (
        ErrMaxTreeDepth      = errors.New("maximum tree depth exceeded")
        ErrFileNotFound      = errors.New("file not found")
        ErrDirectoryNotFound = errors.New("directory not found")
        ErrEntryNotFound     = errors.New("entry not found")
        ErrEntriesNotSorted  = errors.New("entries in tree are not sorted")
)

// Tree is basically like a directory - it references a bunch of other trees
// and/or blobs (i.e. files and sub-directories)
type Tree struct {
        Entries []TreeEntry
        Hash    plumbing.Hash

        s storer.EncodedObjectStorer
        m map[string]*TreeEntry
        t map[string]*Tree // tree path cache
}

// GetTree gets a tree from an object storer and decodes it.
func GetTree(s storer.EncodedObjectStorer, h plumbing.Hash) (*Tree, error) {
        o, err := s.EncodedObject(plumbing.TreeObject, h)
        if err != nil {
                return nil, err
        }

        return DecodeTree(s, o)
}

// DecodeTree decodes an encoded object into a *Tree and associates it to the
// given object storer.
func DecodeTree(s storer.EncodedObjectStorer, o plumbing.EncodedObject) (*Tree, error) {
        t := &Tree{s: s}
        if err := t.Decode(o); err != nil {
                return nil, err
        }

        return t, nil
}

// TreeEntry represents a file
type TreeEntry struct {
        Name string
        Mode filemode.FileMode
        Hash plumbing.Hash
}

// File returns the hash of the file identified by the `path` argument.
// The path is interpreted as relative to the tree receiver.
func (t *Tree) File(path string) (*File, error) {
        e, err := t.FindEntry(path)
        if err != nil {
                return nil, ErrFileNotFound
        }

        blob, err := GetBlob(t.s, e.Hash)
        if err != nil {
                if errors.Is(err, plumbing.ErrObjectNotFound) {
                        return nil, ErrFileNotFound
                }
                return nil, err
        }

        return NewFile(path, e.Mode, blob), nil
}

// Size returns the plaintext size of an object, without reading it
// into memory.
func (t *Tree) Size(path string) (int64, error) {
        e, err := t.FindEntry(path)
        if err != nil {
                return 0, ErrEntryNotFound
        }

        return t.s.EncodedObjectSize(e.Hash)
}

// Tree returns the tree identified by the `path` argument.
// The path is interpreted as relative to the tree receiver.
func (t *Tree) Tree(path string) (*Tree, error) {
        e, err := t.FindEntry(path)
        if err != nil {
                return nil, ErrDirectoryNotFound
        }

        tree, err := GetTree(t.s, e.Hash)
        if errors.Is(err, plumbing.ErrObjectNotFound) {
                return nil, ErrDirectoryNotFound
        }

        return tree, err
}

// TreeEntryFile returns the *File for a given *TreeEntry.
func (t *Tree) TreeEntryFile(e *TreeEntry) (*File, error) {
        blob, err := GetBlob(t.s, e.Hash)
        if err != nil {
                return nil, err
        }

        return NewFile(e.Name, e.Mode, blob), nil
}

// FindEntry search a TreeEntry in this tree or any subtree.
func (t *Tree) FindEntry(path string) (*TreeEntry, error) {
        if t.t == nil {
                t.t = make(map[string]*Tree)
        }

        pathParts := strings.Split(path, "/")
        startingTree := t
        pathCurrent := ""

        // search for the longest path in the tree path cache
        for i := len(pathParts) - 1; i > 1; i-- {
                path := filepath.Join(pathParts[:i]...)

                tree, ok := t.t[path]
                if ok {
                        startingTree = tree
                        pathParts = pathParts[i:]
                        pathCurrent = path

                        break
                }
        }

        var tree *Tree
        var err error
        for tree = startingTree; len(pathParts) > 1; pathParts = pathParts[1:] {
                if tree, err = tree.dir(pathParts[0]); err != nil {
                        return nil, err
                }

                pathCurrent = filepath.Join(pathCurrent, pathParts[0])
                t.t[pathCurrent] = tree
        }

        return tree.entry(pathParts[0])
}

func (t *Tree) dir(baseName string) (*Tree, error) {
        entry, err := t.entry(baseName)
        if err != nil {
                return nil, ErrDirectoryNotFound
        }

        obj, err := t.s.EncodedObject(plumbing.TreeObject, entry.Hash)
        if err != nil {
                return nil, err
        }

        tree := &Tree{s: t.s}
        err = tree.Decode(obj)

        return tree, err
}

func (t *Tree) entry(baseName string) (*TreeEntry, error) {
        if t.m == nil {
                t.buildMap()
        }

        entry, ok := t.m[baseName]
        if !ok {
                return nil, ErrEntryNotFound
        }

        return entry, nil
}

// Files returns a FileIter allowing to iterate over the Tree
func (t *Tree) Files() *FileIter {
        return NewFileIter(t.s, t)
}

// ID returns the object ID of the tree. The returned value will always match
// the current value of Tree.Hash.
//
// ID is present to fulfill the Object interface.
func (t *Tree) ID() plumbing.Hash {
        return t.Hash
}

// Type returns the type of object. It always returns plumbing.TreeObject.
func (t *Tree) Type() plumbing.ObjectType {
        return plumbing.TreeObject
}

// Decode transform an plumbing.EncodedObject into a Tree struct
func (t *Tree) Decode(o plumbing.EncodedObject) (err error) {
        if o.Type() != plumbing.TreeObject {
                return ErrUnsupportedObject
        }

        t.Hash = o.Hash()
        if o.Size() == 0 {
                return nil
        }

        t.Entries = nil
        t.m = nil

        reader, err := o.Reader()
        if err != nil {
                return err
        }
        defer ioutil.CheckClose(reader, &err)

        r := sync.GetBufioReader(reader)
        defer sync.PutBufioReader(r)

        for {
                str, err := r.ReadString(' ')
                if err != nil {
                        if err == io.EOF {
                                break
                        }

                        return err
                }
                str = str[:len(str)-1] // strip last byte (' ')

                mode, err := filemode.New(str)
                if err != nil {
                        return err
                }

                name, err := r.ReadString(0)
                if err != nil && err != io.EOF {
                        return err
                }

                var hash plumbing.Hash
                if _, err = hash.ReadFrom(r); err != nil {
                        return err
                }

                baseName := name[:len(name)-1]
                t.Entries = append(t.Entries, TreeEntry{
                        Hash: hash,
                        Mode: mode,
                        Name: baseName,
                })
        }

        return nil
}

type TreeEntrySorter []TreeEntry

func (s TreeEntrySorter) Len() int {
        return len(s)
}

func (s TreeEntrySorter) Less(i, j int) bool {
        name1 := s[i].Name
        name2 := s[j].Name
        if s[i].Mode == filemode.Dir {
                name1 += "/"
        }
        if s[j].Mode == filemode.Dir {
                name2 += "/"
        }
        return name1 < name2
}

func (s TreeEntrySorter) Swap(i, j int) {
        s[i], s[j] = s[j], s[i]
}

// Encode transforms a Tree into a plumbing.EncodedObject.
// The tree entries must be sorted by name.
func (t *Tree) Encode(o plumbing.EncodedObject) (err error) {
        o.SetType(plumbing.TreeObject)
        w, err := o.Writer()
        if err != nil {
                return err
        }

        defer ioutil.CheckClose(w, &err)

        if !sort.IsSorted(TreeEntrySorter(t.Entries)) {
                return ErrEntriesNotSorted
        }

        for _, entry := range t.Entries {
                if strings.IndexByte(entry.Name, 0) != -1 {
                        return fmt.Errorf("malformed filename %q", entry.Name)
                }
                if _, err = fmt.Fprintf(w, "%o %s", entry.Mode, entry.Name); err != nil {
                        return err
                }

                if _, err = w.Write([]byte{0x00}); err != nil {
                        return err
                }

                if _, err = entry.Hash.WriteTo(w); err != nil {
                        return err
                }
        }

        return err
}

func (t *Tree) buildMap() {
        t.m = make(map[string]*TreeEntry)
        for i := 0; i < len(t.Entries); i++ {
                t.m[t.Entries[i].Name] = &t.Entries[i]
        }
}

// Diff returns a list of changes between this tree and the provided one
func (t *Tree) Diff(to *Tree) (Changes, error) {
        return t.DiffContext(context.Background(), to)
}

// DiffContext returns a list of changes between this tree and the provided one
// Error will be returned if context expires. Provided context must be non nil.
//
// NOTE: Since version 5.1.0 the renames are correctly handled, the settings
// used are the recommended options DefaultDiffTreeOptions.
func (t *Tree) DiffContext(ctx context.Context, to *Tree) (Changes, error) {
        return DiffTreeWithOptions(ctx, t, to, DefaultDiffTreeOptions)
}

// Patch returns a slice of Patch objects with all the changes between trees
// in chunks. This representation can be used to create several diff outputs.
func (t *Tree) Patch(to *Tree) (*Patch, error) {
        return t.PatchContext(context.Background(), to)
}

// PatchContext returns a slice of Patch objects with all the changes between
// trees in chunks. This representation can be used to create several diff
// outputs. If context expires, an error will be returned. Provided context must
// be non-nil.
//
// NOTE: Since version 5.1.0 the renames are correctly handled, the settings
// used are the recommended options DefaultDiffTreeOptions.
func (t *Tree) PatchContext(ctx context.Context, to *Tree) (*Patch, error) {
        changes, err := t.DiffContext(ctx, to)
        if err != nil {
                return nil, err
        }

        return changes.PatchContext(ctx)
}

// treeEntryIter facilitates iterating through the TreeEntry objects in a Tree.
type treeEntryIter struct {
        t   *Tree
        pos int
}

func (iter *treeEntryIter) Next() (TreeEntry, error) {
        if iter.pos >= len(iter.t.Entries) {
                return TreeEntry{}, io.EOF
        }
        iter.pos++
        return iter.t.Entries[iter.pos-1], nil
}

// TreeWalker provides a means of walking through all of the entries in a Tree.
type TreeWalker struct {
        stack     []*treeEntryIter
        base      string
        recursive bool
        seen      map[plumbing.Hash]bool

        s storer.EncodedObjectStorer
        t *Tree
}

// NewTreeWalker returns a new TreeWalker for the given tree.
//
// It is the caller's responsibility to call Close() when finished with the
// tree walker.
func NewTreeWalker(t *Tree, recursive bool, seen map[plumbing.Hash]bool) *TreeWalker {
        stack := make([]*treeEntryIter, 0, startingStackSize)
        stack = append(stack, &treeEntryIter{t, 0})

        return &TreeWalker{
                stack:     stack,
                recursive: recursive,
                seen:      seen,

                s: t.s,
                t: t,
        }
}

// Next returns the next object from the tree. Objects are returned in order
// and subtrees are included. After the last object has been returned further
// calls to Next() will return io.EOF.
//
// In the current implementation any objects which cannot be found in the
// underlying repository will be skipped automatically. It is possible that this
// may change in future versions.
func (w *TreeWalker) Next() (name string, entry TreeEntry, err error) {
        var obj *Tree
        for {
                current := len(w.stack) - 1
                if current < 0 {
                        // Nothing left on the stack so we're finished
                        err = io.EOF
                        return
                }

                if current > maxTreeDepth {
                        // We're probably following bad data or some self-referencing tree
                        err = ErrMaxTreeDepth
                        return
                }

                entry, err = w.stack[current].Next()
                if err == io.EOF {
                        // Finished with the current tree, move back up to the parent
                        w.stack = w.stack[:current]
                        w.base, _ = path.Split(w.base)
                        w.base = strings.TrimSuffix(w.base, "/")
                        continue
                }

                if err != nil {
                        return
                }

                if w.seen[entry.Hash] {
                        continue
                }

                if entry.Mode == filemode.Dir {
                        obj, err = GetTree(w.s, entry.Hash)
                }

                name = simpleJoin(w.base, entry.Name)

                if err != nil {
                        err = io.EOF
                        return
                }

                break
        }

        if !w.recursive {
                return
        }

        if obj != nil {
                w.stack = append(w.stack, &treeEntryIter{obj, 0})
                w.base = simpleJoin(w.base, entry.Name)
        }

        return
}

// Tree returns the tree that the tree walker most recently operated on.
func (w *TreeWalker) Tree() *Tree {
        current := len(w.stack) - 1
        if w.stack[current].pos == 0 {
                current--
        }

        if current < 0 {
                return nil
        }

        return w.stack[current].t
}

// Close releases any resources used by the TreeWalker.
func (w *TreeWalker) Close() {
        w.stack = nil
}

// TreeIter provides an iterator for a set of trees.
type TreeIter struct {
        storer.EncodedObjectIter
        s storer.EncodedObjectStorer
}

// NewTreeIter takes a storer.EncodedObjectStorer and a
// storer.EncodedObjectIter and returns a *TreeIter that iterates over all
// tree contained in the storer.EncodedObjectIter.
//
// Any non-tree object returned by the storer.EncodedObjectIter is skipped.
func NewTreeIter(s storer.EncodedObjectStorer, iter storer.EncodedObjectIter) *TreeIter {
        return &TreeIter{iter, s}
}

// Next moves the iterator to the next tree and returns a pointer to it. If
// there are no more trees, it returns io.EOF.
func (iter *TreeIter) Next() (*Tree, error) {
        for {
                obj, err := iter.EncodedObjectIter.Next()
                if err != nil {
                        return nil, err
                }

                if obj.Type() != plumbing.TreeObject {
                        continue
                }

                return DecodeTree(iter.s, obj)
        }
}

// ForEach call the cb function for each tree contained on this iter until
// an error happens or the end of the iter is reached. If ErrStop is sent
// the iteration is stop but no error is returned. The iterator is closed.
func (iter *TreeIter) ForEach(cb func(*Tree) error) error {
        return iter.EncodedObjectIter.ForEach(func(obj plumbing.EncodedObject) error {
                if obj.Type() != plumbing.TreeObject {
                        return nil
                }

                t, err := DecodeTree(iter.s, obj)
                if err != nil {
                        return err
                }

                return cb(t)
        })
}

func simpleJoin(parent, child string) string {
        if len(parent) > 0 {
                return parent + "/" + child
        }
        return child
}

package object

import (
        "io"

        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/filemode"
        "github.com/go-git/go-git/v6/utils/merkletrie/noder"
)

// A treenoder is a helper type that wraps git trees into merkletrie
// noders.
//
// As a merkletrie noder doesn't understand the concept of modes (e.g.
// file permissions), the treenoder includes the mode of the git tree in
// the hash, so changes in the modes will be detected as modifications
// to the file contents by the merkletrie difftree algorithm.  This is
// consistent with how the "git diff-tree" command works.
type treeNoder struct {
        parent   *Tree  // the root node is its own parent
        name     string // empty string for the root node
        mode     filemode.FileMode
        hash     plumbing.Hash
        children []noder.Noder // memoized
}

// NewTreeRootNode returns the root node of a Tree
func NewTreeRootNode(t *Tree) noder.Noder {
        if t == nil {
                return &treeNoder{}
        }

        return &treeNoder{
                parent: t,
                name:   "",
                mode:   filemode.Dir,
                hash:   t.Hash,
        }
}

func (t *treeNoder) Skip() bool {
        return false
}

func (t *treeNoder) isRoot() bool {
        return t.name == ""
}

func (t *treeNoder) String() string {
        return "treeNoder <" + t.name + ">"
}

func (t *treeNoder) Hash() []byte {
        if t.mode == filemode.Deprecated {
                return append(t.hash.Bytes(), filemode.Regular.Bytes()...)
        }
        return append(t.hash.Bytes(), t.mode.Bytes()...)
}

func (t *treeNoder) Name() string {
        return t.name
}

func (t *treeNoder) IsDir() bool {
        return t.mode == filemode.Dir
}

// Children will return the children of a treenoder as treenoders,
// building them from the children of the wrapped git tree.
func (t *treeNoder) Children() ([]noder.Noder, error) {
        if t.mode != filemode.Dir {
                return noder.NoChildren, nil
        }

        // children are memoized for efficiency
        if t.children != nil {
                return t.children, nil
        }

        // the parent of the returned children will be ourself as a tree if
        // we are a not the root treenoder.  The root is special as it
        // is is own parent.
        parent := t.parent
        if !t.isRoot() {
                var err error
                if parent, err = t.parent.Tree(t.name); err != nil {
                        return nil, err
                }
        }

        var err error
        t.children, err = transformChildren(parent)
        return t.children, err
}

// Returns the children of a tree as treenoders.
// Efficiency is key here.
func transformChildren(t *Tree) ([]noder.Noder, error) {
        var err error
        var e TreeEntry

        // there will be more tree entries than children in the tree,
        // due to submodules and empty directories, but I think it is still
        // worth it to pre-allocate the whole array now, even if sometimes
        // is bigger than needed.
        ret := make([]noder.Noder, 0, len(t.Entries))

        walker := NewTreeWalker(t, false, nil) // don't recurse
        // don't defer walker.Close() for efficiency reasons.
        for {
                _, e, err = walker.Next()
                if err == io.EOF {
                        break
                }
                if err != nil {
                        walker.Close()
                        return nil, err
                }

                ret = append(ret, &treeNoder{
                        parent: t,
                        name:   e.Name,
                        mode:   e.Mode,
                        hash:   e.Hash,
                })
        }
        walker.Close()

        return ret, nil
}

// len(t.tree.Entries) != the number of elements walked by treewalker
// for some reason because of empty directories, submodules, etc, so we
// have to walk here.
func (t *treeNoder) NumChildren() (int, error) {
        children, err := t.Children()
        if err != nil {
                return 0, err
        }

        return len(children), nil
}

// Package transport implements the git pack protocol with a pluggable
// This is a low-level package to implement new transports. Use a concrete
// implementation instead (e.g. http, file, ssh).
//
// A simple example of usage can be found in the file package.
package transport

import (
        "context"
        "errors"
        "io"
        "regexp"

        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/protocol"
        "github.com/go-git/go-git/v6/plumbing/protocol/packp"
        "github.com/go-git/go-git/v6/plumbing/protocol/packp/capability"
        "github.com/go-git/go-git/v6/plumbing/protocol/packp/sideband"
        "github.com/go-git/go-git/v6/storage"
)

const (
        readErrorSecondsTimeout = 10
)

var (
        // ErrUnsupportedVersion is returned when the protocol version is not
        // supported.
        ErrUnsupportedVersion = errors.New("unsupported protocol version")
        // ErrUnsupportedService is returned when the service is not supported.
        ErrUnsupportedService = errors.New("unsupported service")
        // ErrInvalidResponse is returned when the response is invalid.
        ErrInvalidResponse = errors.New("invalid response")
        // ErrTimeoutExceeded is returned when the timeout is exceeded.
        ErrTimeoutExceeded = errors.New("timeout exceeded")
        // ErrPackedObjectsNotSupported is returned when the server does not support
        // packed objects.
        ErrPackedObjectsNotSupported = errors.New("packed objects not supported")
        // stdErrSkipPattern is used for skipping lines from a command's stderr output.
        // Any line matching this pattern will be skipped from further
        // processing and not be returned to calling code.
        stdErrSkipPattern = regexp.MustCompile("^remote:( =*){0,1}$")
)

// RemoteError represents an error returned by the remote.
// TODO: embed error
type RemoteError struct {
        Reason string
}

// Error implements the error interface.
func (e *RemoteError) Error() string {
        return e.Reason
}

// NewRemoteError creates a new RemoteError.
func NewRemoteError(reason string) error {
        return &RemoteError{Reason: reason}
}

// Connection represents a session endpoint connection.
type Connection interface {
        // Close closes the connection.
        Close() error

        // Capabilities returns the list of capabilities supported by the server.
        Capabilities() *capability.List

        // Version returns the Git protocol version the server supports.
        Version() protocol.Version

        // StatelessRPC indicates that the connection is a half-duplex connection
        // and should operate in half-duplex mode i.e. performs a single read-write
        // cycle. This fits with the HTTP POST request process where session may
        // read the request, write a response, and exit.
        StatelessRPC() bool

        // GetRemoteRefs returns the references advertised by the remote.
        // Using protocol v0 or v1, this returns the references advertised by the
        // remote during the handshake. Using protocol v2, this runs the ls-refs
        // command on the remote.
        // This will error if the session is not already established using
        // Handshake.
        GetRemoteRefs(ctx context.Context) ([]*plumbing.Reference, error)

        // Fetch sends a fetch-pack request to the server.
        Fetch(ctx context.Context, req *FetchRequest) error

        // Push sends a send-pack request to the server.
        Push(ctx context.Context, req *PushRequest) error
}

var _ io.Closer = Connection(nil)

// FetchRequest contains the parameters for a fetch-pack request.
// This is used during the pack negotiation phase of the fetch operation.
// See https://git-scm.com/docs/pack-protocol#_packfile_negotiation
type FetchRequest struct {
        // Progress is the progress sideband.
        Progress sideband.Progress

        // Wants is the list of references to fetch.
        // TODO: Build this slice in the transport package.
        Wants []plumbing.Hash

        // Haves is the list of references the client already has.
        // TODO: Build this slice in the transport package.
        Haves []plumbing.Hash

        // Depth is the depth of the fetch.
        Depth int

        // Filter holds the filters to be applied when deciding what
        // objects will be added to the packfile.
        Filter packp.Filter

        // IncludeTags indicates whether tags should be fetched.
        IncludeTags bool
}

// PushRequest contains the parameters for a push request.
type PushRequest struct {
        // Packfile is the packfile reader.
        Packfile io.ReadCloser

        // Commands is the list of push commands to be sent to the server.
        // TODO: build the Commands slice in the transport package.
        Commands []*packp.Command

        // Progress is the progress sideband.
        Progress sideband.Progress

        // Options is a set of push-options to be sent to the server during push.
        Options []string

        // Atomic indicates an atomic push.
        // If the server supports atomic push, it will update the refs in one
        // atomic transaction. Either all refs are updated or none.
        Atomic bool
}

// Session is a Git protocol transfer session.
// This is used by all protocols.
type Session interface {
        // Handshake starts the negotiation with the remote to get version if not
        // already connected.
        // Params are the optional extra parameters to be sent to the server. Use
        // this to send the protocol version of the client and any other extra parameters.
        Handshake(ctx context.Context, service Service, params ...string) (Connection, error)
}

// Commander creates Command instances. This is the main entry point for
// transport implementations.
type Commander interface {
        // Connect creates a new Command for the given git command and
        // endpoint. cmd can be git-upload-pack or git-receive-pack. An
        // error should be returned if the endpoint is not supported or the
        // command cannot be created (e.g. binary does not exist, connection
        // cannot be established).
        Command(ctx context.Context, cmd string, ep *Endpoint, auth AuthMethod, params ...string) (Command, error)
}

// Command is used for a single command execution.
// This interface is modeled after exec.Cmd and ssh.Session in the standard
// library.
type Command interface {
        // StderrPipe returns a pipe that will be connected to the command's
        // standard error when the command starts. It should not be called after
        // Start.
        StderrPipe() (io.Reader, error)
        // StdinPipe returns a pipe that will be connected to the command's
        // standard input when the command starts. It should not be called after
        // Start. The pipe should be closed when no more input is expected.
        StdinPipe() (io.WriteCloser, error)
        // StdoutPipe returns a pipe that will be connected to the command's
        // standard output when the command starts. It should not be called after
        // Start.
        StdoutPipe() (io.Reader, error)
        // Start starts the specified command. It does not wait for it to
        // complete.
        Start() error
        // Close closes the command and releases any resources used by it. It
        // will block until the command exits.
        Close() error
}

// CommandKiller expands the Command interface, enabling it for being killed.
type CommandKiller interface {
        // Kill and close the session whatever the state it is. It will block until
        // the command is terminated.
        Kill() error
}

type client struct {
        cmdr Commander
}

// NewPackTransport creates a new client using the given Commander.
func NewPackTransport(runner Commander) Transport {
        return &client{runner}
}

// NewSession returns a new session for an endpoint.
func (c *client) NewSession(st storage.Storer, ep *Endpoint, auth AuthMethod) (Session, error) {
        return NewPackSession(st, ep, auth, c.cmdr)
}

// SupportedProtocols returns a list of supported Git protocol versions by
// the transport client.
func (c *client) SupportedProtocols() []protocol.Version {
        return []protocol.Version{
                protocol.V0,
                protocol.V1,
        }
}

package transport

import (
        "context"
        "io"

        "github.com/go-git/go-git/v6/plumbing/format/packfile"
        "github.com/go-git/go-git/v6/plumbing/protocol/packp"
        "github.com/go-git/go-git/v6/plumbing/protocol/packp/capability"
        "github.com/go-git/go-git/v6/plumbing/protocol/packp/sideband"
        "github.com/go-git/go-git/v6/storage"
        "github.com/go-git/go-git/v6/utils/ioutil"
)

// FetchPack fetches a packfile from the remote connection into the given
// storage repository and updates the shallow information.
func FetchPack(
        ctx context.Context,
        st storage.Storer,
        conn Connection,
        packf io.ReadCloser,
        shallowInfo *packp.ShallowUpdate,
        req *FetchRequest,
) (err error) {
        packf = ioutil.NewContextReadCloser(ctx, packf)

        // Do we have sideband enabled?
        var demuxer *sideband.Demuxer
        var reader io.Reader = packf
        caps := conn.Capabilities()
        if caps.Supports(capability.Sideband64k) {
                demuxer = sideband.NewDemuxer(sideband.Sideband64k, reader)
        } else if caps.Supports(capability.Sideband) {
                demuxer = sideband.NewDemuxer(sideband.Sideband, reader)
        }

        if demuxer != nil && req.Progress != nil {
                demuxer.Progress = req.Progress
                reader = demuxer
        }

        if err := packfile.UpdateObjectStorage(st, reader); err != nil {
                return err
        }

        if err := packf.Close(); err != nil {
                return err
        }

        // Update shallow
        if shallowInfo != nil {
                if err := updateShallow(st, shallowInfo); err != nil {
                        return err
                }
        }

        return nil
}

func updateShallow(st storage.Storer, shallowInfo *packp.ShallowUpdate) error {
        shallows, err := st.Shallow()
        if err != nil {
                return err
        }

outer:
        for _, s := range shallowInfo.Shallows {
                for _, oldS := range shallows {
                        if s == oldS {
                                continue outer
                        }
                }
                shallows = append(shallows, s)
        }

        // unshallow commits
        for _, s := range shallowInfo.Unshallows {
                for i, oldS := range shallows {
                        if s == oldS {
                                shallows = append(shallows[:i], shallows[i+1:]...)
                                break
                        }
                }
        }

        return st.SetShallow(shallows)
}

package transport

import (
        "path/filepath"

        "github.com/go-git/go-git/v6/plumbing/cache"
        "github.com/go-git/go-git/v6/plumbing/storer"
        "github.com/go-git/go-git/v6/storage"
        "github.com/go-git/go-git/v6/storage/filesystem"

        "github.com/go-git/go-billy/v5"
        "github.com/go-git/go-billy/v5/osfs"
)

// DefaultLoader is a filesystem loader ignoring host and resolving paths to /.
var DefaultLoader = NewFilesystemLoader(osfs.New(""), false)

// Loader loads repository's storer.Storer based on an optional host and a path.
type Loader interface {
        // Load loads a storer.Storer given a transport.Endpoint.
        // Returns transport.ErrRepositoryNotFound if the repository does not
        // exist.
        Load(ep *Endpoint) (storage.Storer, error)
}

// FilesystemLoader is a Loader that uses a billy.Filesystem to load
// repositories from the file system. It ignores the host and resolves paths to
// the given base filesystem.
type FilesystemLoader struct {
        base   billy.Filesystem
        strict bool
}

// NewFilesystemLoader creates a Loader that ignores host and resolves paths
// with a given base filesystem.
func NewFilesystemLoader(base billy.Filesystem, strict bool) Loader {
        return &FilesystemLoader{base, strict}
}

// Load looks up the endpoint's path in the base file system and returns a
// storer for it. Returns transport.ErrRepositoryNotFound if a repository does
// not exist in the given path.
func (l *FilesystemLoader) Load(ep *Endpoint) (storage.Storer, error) {
        return l.load(ep, false)
}

func (l *FilesystemLoader) load(ep *Endpoint, tried bool) (storage.Storer, error) {
        fs, err := l.base.Chroot(ep.Path)
        if err != nil {
                return nil, err
        }

        if _, err := fs.Stat("config"); err != nil {
                if !l.strict && !tried {
                        if fi, err := fs.Stat(".git"); err == nil && fi.IsDir() {
                                ep.Path = filepath.Join(ep.Path, ".git")
                        } else {
                                ep.Path = ep.Path + ".git"
                        }
                        return l.load(ep, true)
                }
                return nil, ErrRepositoryNotFound
        }

        return filesystem.NewStorage(fs, cache.NewObjectLRUDefault()), nil
}

// MapLoader is a Loader that uses a lookup map of storer.Storer by
// transport.Endpoint.
type MapLoader map[string]storer.Storer

// Load returns a storer.Storer for given a transport.Endpoint by looking it up
// in the map. Returns transport.ErrRepositoryNotFound if the endpoint does not
// exist.
func (l MapLoader) Load(ep *Endpoint) (storer.Storer, error) {
        s, ok := l[ep.String()]
        if !ok {
                return nil, ErrRepositoryNotFound
        }

        return s, nil
}

package transport

import (
        "bytes"
        "context"
        "io"

        "github.com/go-git/go-git/v6/utils/ioutil"
)

type mockCommand struct {
        stdin  bytes.Buffer
        stdout bytes.Buffer
        stderr bytes.Buffer
}

func (c mockCommand) StderrPipe() (io.Reader, error) {
        return &c.stderr, nil
}

func (c mockCommand) StdinPipe() (io.WriteCloser, error) {
        return ioutil.WriteNopCloser(&c.stdin), nil
}

func (c mockCommand) StdoutPipe() (io.Reader, error) {
        return &c.stdout, nil
}

func (c mockCommand) Start() error {
        return nil
}

func (c mockCommand) Close() error {
        return nil
}

type mockCommander struct {
        stderr string
}

func (c mockCommander) Command(_ context.Context, cmd string, ep *Endpoint, auth AuthMethod, _ ...string) (Command, error) {
        return &mockCommand{
                stderr: *bytes.NewBufferString(c.stderr),
        }, nil
}

package transport

import (
        "context"
        "errors"
        "fmt"
        "io"

        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/format/pktline"
        "github.com/go-git/go-git/v6/plumbing/protocol/packp"
        "github.com/go-git/go-git/v6/plumbing/protocol/packp/capability"
        "github.com/go-git/go-git/v6/storage"
        "github.com/go-git/go-git/v6/utils/ioutil"
)

var (
        ErrFilterNotSupported  = errors.New("server does not support filters")
        ErrShallowNotSupported = errors.New("server does not support shallow clients")
)

// NegotiatePack returns the result of the pack negotiation phase of the fetch operation.
// See https://git-scm.com/docs/pack-protocol#_packfile_negotiation
func NegotiatePack(
        ctx context.Context,
        st storage.Storer,
        conn Connection,
        reader io.Reader,
        writer io.WriteCloser,
        req *FetchRequest,
) (shallowInfo *packp.ShallowUpdate, err error) {
        reader = ioutil.NewContextReader(ctx, reader)
        writer = ioutil.NewContextWriteCloser(ctx, writer)
        caps := conn.Capabilities()

        // Create upload-request
        upreq := packp.NewUploadRequest()
        multiAck := caps.Supports(capability.MultiACK)
        multiAckDetailed := caps.Supports(capability.MultiACKDetailed)
        if multiAckDetailed {
                upreq.Capabilities.Set(capability.MultiACKDetailed) // nolint: errcheck
        } else if multiAck {
                upreq.Capabilities.Set(capability.MultiACK) // nolint: errcheck
        }

        if req.Progress != nil {
                if caps.Supports(capability.Sideband64k) {
                        upreq.Capabilities.Set(capability.Sideband64k) // nolint: errcheck
                } else if caps.Supports(capability.Sideband) {
                        upreq.Capabilities.Set(capability.Sideband) // nolint: errcheck
                }
        } else if caps.Supports(capability.NoProgress) {
                upreq.Capabilities.Set(capability.NoProgress) // nolint: errcheck
        }

        // TODO: support thin-pack
        // if caps.Supports(capability.ThinPack) {
        //         upreq.Capabilities.Set(capability.ThinPack) // nolint: errcheck
        // }

        if caps.Supports(capability.OFSDelta) {
                upreq.Capabilities.Set(capability.OFSDelta) // nolint: errcheck
        }

        if caps.Supports(capability.Agent) {
                upreq.Capabilities.Set(capability.Agent, capability.DefaultAgent()) // nolint: errcheck
        }

        if req.IncludeTags && caps.Supports(capability.IncludeTag) {
                upreq.Capabilities.Set(capability.IncludeTag) // nolint: errcheck
        }

        if req.Filter != "" {
                if caps.Supports(capability.Filter) {
                        upreq.Filter = req.Filter
                        if err := upreq.Capabilities.Set(capability.Filter); err != nil {
                                return nil, err
                        }
                } else {
                        return nil, ErrFilterNotSupported
                }
        }

        upreq.Wants = req.Wants

        if req.Depth > 0 {
                if !caps.Supports(capability.Shallow) {
                        return nil, ErrShallowNotSupported
                }

                upreq.Depth = packp.DepthCommits(req.Depth)
                upreq.Shallows, err = st.Shallow()
                if err != nil {
                        return nil, err
                }
        }

        // Note: empty request means haves are a subset of wants, in that case we have
        // everything we asked for. Close the connection and return nil.
        if isSubset(req.Wants, req.Haves) && len(upreq.Shallows) == 0 {
                if err := pktline.WriteFlush(writer); err != nil {
                        return nil, err
                }

                // Close the writer to signal the end of the request
                if err := writer.Close(); err != nil {
                        return nil, fmt.Errorf("closing writer: %s", err)
                }

                return nil, ErrNoChange
        }

        // Create upload-haves
        common := map[plumbing.Hash]struct{}{}

        var inVein int
        var done bool
        var gotContinue bool // whether we got a continue from the server
        firstRound := true
        for !done {
                // Pop the last 32 or depth have commits from the pending list and
                // insert their parents into the pending list.
                // TODO: Properly build and implement haves negotiation, and move it
                // from remote.go to this package.
                var uphav packp.UploadHaves
                for i := 0; i < 32 && len(req.Haves) > 0; i++ {
                        uphav.Haves = append(uphav.Haves, req.Haves[len(req.Haves)-1])
                        req.Haves = req.Haves[:len(req.Haves)-1]
                        inVein++
                }

                // Let the server know we're done
                const maxInVein = 256
                done = len(req.Haves) == 0 || (gotContinue && inVein >= maxInVein)
                uphav.Done = done

                // Note: empty request means haves are a subset of wants, in that case we have
                // everything we asked for. Close the connection and return nil.
                if isSubset(req.Wants, uphav.Haves) && len(upreq.Shallows) == 0 {
                        if err := pktline.WriteFlush(writer); err != nil {
                                return nil, err
                        }

                        // Close the writer to signal the end of the request
                        if err := writer.Close(); err != nil {
                                return nil, fmt.Errorf("closing writer: %s", err)
                        }

                        return nil, ErrNoChange
                }

                // Begin the upload-pack negotiation
                if firstRound || conn.StatelessRPC() {
                        if err := upreq.Encode(writer); err != nil {
                                return nil, fmt.Errorf("sending upload-request: %w", err)
                        }
                }

                readc := make(chan error)
                if !conn.StatelessRPC() {
                        go func() { readc <- readShallows(conn, reader, req, &shallowInfo, firstRound) }()
                }

                // Encode upload-haves
                if err := uphav.Encode(writer); err != nil {
                        return nil, fmt.Errorf("sending upload-haves: %w", err)
                }

                // Close the writer to signal the end of the request
                if conn.StatelessRPC() {
                        if err := writer.Close(); err != nil {
                                return nil, fmt.Errorf("closing writer: %w", err)
                        }

                        if err := readShallows(conn, reader, req, &shallowInfo, firstRound); err != nil {
                                return nil, err
                        }
                } else {
                        // Wait for the read channel to be closed
                        if err := <-readc; err != nil {
                                return nil, err
                        }
                }

                go func() {
                        defer close(readc)

                        if done || len(uphav.Haves) > 0 {
                                var srvrs packp.ServerResponse
                                if err := srvrs.Decode(reader); err != nil {
                                        readc <- fmt.Errorf("decoding server-response: %w", err)
                                        return
                                }

                                for _, ack := range srvrs.ACKs {
                                        if !gotContinue && ack.Status > 0 {
                                                gotContinue = true
                                        }
                                        if ack.Status == packp.ACKCommon {
                                                common[ack.Hash] = struct{}{}
                                        }
                                }
                        }

                        readc <- nil
                }()

                // Wait for the read channel to be closed
                if err := <-readc; err != nil {
                        return nil, err
                }

                firstRound = false
        }

        if !conn.StatelessRPC() {
                if err := writer.Close(); err != nil {
                        return nil, fmt.Errorf("closing writer: %w", err)
                }
        }

        return shallowInfo, nil
}

func isSubset(needle []plumbing.Hash, haystack []plumbing.Hash) bool {
        for _, h := range needle {
                found := false
                for _, oh := range haystack {
                        if h == oh {
                                found = true
                                break
                        }
                }

                if !found {
                        return false
                }
        }

        return true
}

func readShallows(
        conn Connection,
        r io.Reader,
        req *FetchRequest,
        shallowInfo **packp.ShallowUpdate,
        firstRound bool,
) error {
        // Decode shallow-update
        // If depth is not zero, then we expect a shallow update from the
        // server.
        if (firstRound || conn.StatelessRPC()) && req.Depth > 0 {
                var shupd packp.ShallowUpdate
                if err := shupd.Decode(r); err != nil {
                        return fmt.Errorf("decoding shallow-update: %w", err)
                }

                // Only return the first shallow update
                if shallowInfo == nil {
                        shallowInfo = new(*packp.ShallowUpdate)
                        *shallowInfo = &shupd
                }
        }

        return nil
}

package transport

import (
        "bufio"
        "bytes"
        "context"
        "io"
        "strings"

        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/protocol"
        "github.com/go-git/go-git/v6/plumbing/protocol/packp"
        "github.com/go-git/go-git/v6/plumbing/protocol/packp/capability"
        "github.com/go-git/go-git/v6/storage"
        "github.com/go-git/go-git/v6/utils/ioutil"
)

// NewPackSession creates a new session that implements a full-duplex Git pack protocol.
func NewPackSession(
        st storage.Storer,
        ep *Endpoint,
        auth AuthMethod,
        cmdr Commander,
) (Session, error) {
        ps := &PackSession{
                ep:   ep,
                auth: auth,
                cmdr: cmdr,
                st:   st,
        }
        return ps, nil
}

// PackSession is a session that implements a full-duplex Git pack transport.
type PackSession struct {
        cmdr Commander
        ep   *Endpoint
        auth AuthMethod
        st   storage.Storer
}

var _ Session = &PackSession{}

// Handshake implements Session.
func (p *PackSession) Handshake(ctx context.Context, service Service, params ...string) (conn Connection, err error) {
        switch service {
        case UploadPackService, ReceivePackService:
                // do nothing
        default:
                return nil, ErrUnsupportedService
        }
        cmd, err := p.cmdr.Command(ctx, service.String(), p.ep, p.auth, params...)
        if err != nil {
                return nil, err
        }

        c := &packConnection{
                st:  p.st,
                cmd: cmd,
                svc: service,
        }

        // Check if the context is already done before starting the command.
        if ctx.Err() != nil {
                return nil, ctx.Err()
        }

        stdin, err := cmd.StdinPipe()
        if err != nil {
                return nil, err
        }

        c.w = stdin

        stdout, err := cmd.StdoutPipe()
        if err != nil {
                return nil, err
        }

        cr := ioutil.NewContextReaderWithCloser(ctx, stdout, cmd)
        c.r = bufio.NewReader(cr)

        stderr, err := cmd.StderrPipe()
        if err != nil {
                return nil, err
        }

        // Some transports like Git doesn't support stderr, so we need to check if
        // it's not nil before starting to read it.
        if stderr != nil {
                go io.Copy(&c.stderrBuf, stderr) // nolint: errcheck
        }

        // Check if stderr is not empty before returning.
        defer func() { checkError(c.stderr(), &err) }()

        if err := cmd.Start(); err != nil {
                return nil, err
        }

        c.version, err = DiscoverVersion(c.r)
        if err != nil {
                return nil, err
        }

        switch c.version {
        case protocol.V2:
                return nil, ErrUnsupportedVersion
        case protocol.V1:
                // Read the version line
                fallthrough
        case protocol.V0:
        }

        ar := packp.NewAdvRefs()
        if err := ar.Decode(c.r); err != nil {
                return nil, err
        }

        c.refs = ar
        c.caps = ar.Capabilities

        return c, nil
}

// packConnection is a convenience type that implements io.ReadWriteCloser.
type packConnection struct {
        st        storage.Storer
        cmd       Command
        svc       Service
        w         io.WriteCloser // stdin
        r         *bufio.Reader  // stdout
        stderrBuf bytes.Buffer

        version protocol.Version
        caps    *capability.List
        refs    *packp.AdvRefs
}

var _ Connection = &packConnection{}

// stderr returns stderr of the command if it's not empty. This will always
// return a RemoteError.
func (p *packConnection) stderr() error {
        s := strings.TrimSpace(p.stderrBuf.String())
        if s == "" {
                return nil
        }

        return NewRemoteError(s)
}

// Close implements Connection.
func (p *packConnection) Close() error {
        return p.cmd.Close()
}

// Capabilities implements Connection.
func (p *packConnection) Capabilities() *capability.List {
        return p.caps
}

// GetRemoteRefs implements Connection.
func (p *packConnection) GetRemoteRefs(ctx context.Context) ([]*plumbing.Reference, error) {
        if p.refs == nil {
                // TODO: return appropriate error
                return nil, ErrEmptyRemoteRepository
        }

        // Some servers like jGit, announce capabilities instead of returning an
        // packp message with a flush. This verifies that we received a empty
        // adv-refs, even if it contains capabilities.
        forPush := p.svc == ReceivePackService
        if !forPush && p.refs.IsEmpty() {
                return nil, ErrEmptyRemoteRepository
        }

        return p.refs.MakeReferenceSlice()
}

// Version implements Connection.
func (p *packConnection) Version() protocol.Version {
        return p.version
}

// StatelessRPC implements Connection.
func (*packConnection) StatelessRPC() bool {
        return false
}

// Fetch implements Connection.
func (p *packConnection) Fetch(ctx context.Context, req *FetchRequest) (err error) {
        shallows, err := NegotiatePack(ctx, p.st, p, p.r, p.w, req)
        if err != nil {
                return err
        }

        return FetchPack(ctx, p.st, p, io.NopCloser(p.r), shallows, req)
}

// Push implements Connection.
func (p *packConnection) Push(ctx context.Context, req *PushRequest) (err error) {
        return SendPack(ctx, p.st, p, p.w, io.NopCloser(p.r), req)
}

// checkError checks if the error is not nil updates the pointer with the
// error.
func checkError(err error, perr *error) {
        if err != nil {
                *perr = err
        }
}

package transport

import (
        "context"
        "fmt"
        "io"

        "github.com/go-git/go-git/v6/plumbing/protocol/packp"
        "github.com/go-git/go-git/v6/plumbing/protocol/packp/capability"
        "github.com/go-git/go-git/v6/plumbing/protocol/packp/sideband"
        "github.com/go-git/go-git/v6/storage"
        "github.com/go-git/go-git/v6/utils/ioutil"
)

// buildUpdateRequests constructs a new update-requests object for the given
// connection and push request.
func buildUpdateRequests(caps *capability.List, req *PushRequest) *packp.UpdateRequests {
        upreq := packp.NewUpdateRequests()

        // The reference discovery phase is done nearly the same way as it is in
        // the fetching protocol. Each reference obj-id and name on the server is
        // sent in packet-line format to the client, followed by a flush-pkt. The
        // only real difference is that the capability listing is different - the
        // only possible values are report-status, report-status-v2, delete-refs,
        // ofs-delta, atomic and push-options.
        for _, cap := range []capability.Capability{
                capability.ReportStatus,
                // TODO: support report-status-v2
                // capability.ReportStatusV2,
                capability.DeleteRefs,
                capability.OFSDelta,

                // This is set later if options are present.
                // capability.PushOptions,
        } {
                if caps.Supports(cap) {
                        upreq.Capabilities.Set(cap) //nolint:errcheck
                }
        }

        if req.Atomic && caps.Supports(capability.Atomic) {
                upreq.Capabilities.Set(capability.Atomic) //nolint:errcheck
        }

        upreq.Commands = req.Commands

        return upreq
}

// SendPack is a function that sends a packfile to a remote server.
func SendPack(
        ctx context.Context,
        st storage.Storer,
        conn Connection,
        writer io.WriteCloser,
        reader io.ReadCloser,
        req *PushRequest,
) error {
        writer = ioutil.NewContextWriteCloser(ctx, writer)
        reader = ioutil.NewContextReadCloser(ctx, reader)

        var needPackfile bool
        for _, cmd := range req.Commands {
                if cmd.Action() != packp.Delete {
                        needPackfile = true
                        break
                }
        }

        if !needPackfile && req.Packfile != nil {
                return fmt.Errorf("packfile is not accepted for push request without new objects")
        }
        if needPackfile && req.Packfile == nil {
                return fmt.Errorf("packfile is required for push request with new objects")
        }

        caps := conn.Capabilities()
        upreq := buildUpdateRequests(caps, req)
        usePushOptions := len(req.Options) > 0 && caps.Supports(capability.PushOptions)
        if usePushOptions {
                upreq.Capabilities.Set(capability.PushOptions) //nolint:errcheck
        }

        if err := upreq.Encode(writer); err != nil {
                return err
        }

        if usePushOptions {
                var opts packp.PushOptions
                opts.Options = req.Options
                if err := opts.Encode(writer); err != nil {
                        return fmt.Errorf("encoding push-options: %w", err)
                }
        }

        // Send the packfile.
        if req.Packfile != nil {
                if _, err := io.Copy(writer, req.Packfile); err != nil {
                        return err
                }

                if err := req.Packfile.Close(); err != nil {
                        return fmt.Errorf("closing packfile: %w", err)
                }
        }

        // Close the write pipe to signal the end of the request.
        if err := writer.Close(); err != nil {
                return err
        }

        if !caps.Supports(capability.ReportStatus) {
                // If we don't have report-status, we're done here.
                return nil
        }

        var r io.Reader = reader
        if req.Progress != nil {
                var d *sideband.Demuxer
                if caps.Supports(capability.Sideband64k) {
                        d = sideband.NewDemuxer(sideband.Sideband64k, reader)
                } else if caps.Supports(capability.Sideband) {
                        d = sideband.NewDemuxer(sideband.Sideband, reader)
                }
                if d != nil {
                        d.Progress = req.Progress
                        r = d
                }
        }

        report := packp.NewReportStatus()
        if err := report.Decode(r); err != nil {
                return fmt.Errorf("decode report-status: %w", err)
        }

        if err := reader.Close(); err != nil {
                return fmt.Errorf("closing reader: %w", err)
        }

        return report.Error()
}

package transport

import (
        "bufio"
        "context"
        "fmt"
        "io"

        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/format/packfile"
        "github.com/go-git/go-git/v6/plumbing/format/pktline"
        "github.com/go-git/go-git/v6/plumbing/protocol"
        "github.com/go-git/go-git/v6/plumbing/protocol/packp"
        "github.com/go-git/go-git/v6/plumbing/protocol/packp/capability"
        "github.com/go-git/go-git/v6/plumbing/protocol/packp/sideband"
        "github.com/go-git/go-git/v6/plumbing/storer"
        "github.com/go-git/go-git/v6/storage"
        "github.com/go-git/go-git/v6/utils/ioutil"
)

// ReceivePackOptions is a set of options for the ReceivePack service.
type ReceivePackOptions struct {
        GitProtocol   string
        AdvertiseRefs bool
        StatelessRPC  bool
}

// ReceivePack is a server command that serves the receive-pack service.
// TODO: support hooks
func ReceivePack(
        ctx context.Context,
        st storage.Storer,
        r io.ReadCloser,
        w io.WriteCloser,
        opts *ReceivePackOptions,
) error {
        if w == nil {
                return fmt.Errorf("nil writer")
        }

        w = ioutil.NewContextWriteCloser(ctx, w)

        if opts == nil {
                opts = &ReceivePackOptions{}
        }

        if opts.AdvertiseRefs || !opts.StatelessRPC {
                switch version := ProtocolVersion(opts.GitProtocol); version {
                case protocol.V1:
                        if _, err := pktline.Writef(w, "version %d\n", version); err != nil {
                                return err
                        }
                // TODO: support version 2
                case protocol.V0, protocol.V2:
                default:
                        return fmt.Errorf("%w: %q", ErrUnsupportedVersion, version)
                }

                if err := AdvertiseReferences(ctx, st, w, ReceivePackService, opts.StatelessRPC); err != nil {
                        return err
                }
        }

        if opts.AdvertiseRefs {
                // Done, there's nothing else to do
                return nil
        }

        if r == nil {
                return fmt.Errorf("nil reader")
        }

        r = ioutil.NewContextReadCloser(ctx, r)

        rd := bufio.NewReader(r)
        l, _, err := pktline.PeekLine(rd)
        if err != nil {
                return err
        }

        // At this point, if we get a flush packet, it means the client
        // has nothing to send, so we can return early.
        if l == pktline.Flush {
                return nil
        }

        updreq := packp.NewUpdateRequests()
        if err := updreq.Decode(rd); err != nil {
                return err
        }

        var (
                caps         = updreq.Capabilities
                needPackfile bool
                pushOpts     packp.PushOptions
        )

        // TODO: Pass the options to the server-side hooks.
        if updreq.Capabilities.Supports(capability.PushOptions) {
                if err := pushOpts.Decode(rd); err != nil {
                        return fmt.Errorf("decoding push-options: %w", err)
                }
        }

        // Should we expect a packfile?
        for _, cmd := range updreq.Commands {
                if cmd.Action() != packp.Delete {
                        needPackfile = true
                        break
                }
        }

        // Receive the packfile
        var unpackErr error
        if needPackfile {
                unpackErr = packfile.UpdateObjectStorage(st, rd)
        }

        // Done with the request, now close the reader
        // to indicate that we are done reading from it.
        if err := r.Close(); err != nil {
                return fmt.Errorf("closing reader: %w", err)
        }

        // Report status if the client supports it
        if !updreq.Capabilities.Supports(capability.ReportStatus) {
                return unpackErr
        }

        var (
                useSideband bool
                writer      io.Writer = w
        )
        if !caps.Supports(capability.NoProgress) {
                if caps.Supports(capability.Sideband64k) {
                        writer = sideband.NewMuxer(sideband.Sideband64k, w)
                        useSideband = true
                } else if caps.Supports(capability.Sideband) {
                        writer = sideband.NewMuxer(sideband.Sideband, w)
                        useSideband = true
                }
        }

        writeCloser := ioutil.NewWriteCloser(writer, w)
        if unpackErr != nil {
                res := sendReportStatus(writeCloser, unpackErr, nil)
                closeWriter(w)
                return res
        }

        var firstErr error
        cmdStatus := make(map[plumbing.ReferenceName]error)
        updateReferences(st, updreq, cmdStatus, &firstErr)

        if err := sendReportStatus(writeCloser, firstErr, cmdStatus); err != nil {
                return err
        }

        if useSideband {
                if err := pktline.WriteFlush(w); err != nil {
                        return fmt.Errorf("flushing sideband: %w", err)
                }
        }
        if firstErr != nil {
                return firstErr
        }
        return closeWriter(w)
}

func closeWriter(w io.WriteCloser) error {
        if err := w.Close(); err != nil {
                return fmt.Errorf("closing writer: %w", err)
        }
        return nil
}

func sendReportStatus(w io.WriteCloser, unpackErr error, cmdStatus map[plumbing.ReferenceName]error) error {
        rs := packp.NewReportStatus()
        rs.UnpackStatus = "ok"
        if unpackErr != nil {
                rs.UnpackStatus = unpackErr.Error()
        }

        for ref, err := range cmdStatus {
                msg := "ok"
                if err != nil {
                        msg = err.Error()
                }
                status := &packp.CommandStatus{
                        ReferenceName: ref,
                        Status:        msg,
                }
                rs.CommandStatuses = append(rs.CommandStatuses, status)
        }

        if err := rs.Encode(w); err != nil {
                return err
        }

        return nil
}

func setStatus(cmdStatus map[plumbing.ReferenceName]error, firstErr *error, ref plumbing.ReferenceName, err error) {
        cmdStatus[ref] = err
        if *firstErr == nil && err != nil {
                *firstErr = err
        }
}

func referenceExists(s storer.ReferenceStorer, n plumbing.ReferenceName) (bool, error) {
        _, err := s.Reference(n)
        if err == plumbing.ErrReferenceNotFound {
                return false, nil
        }

        return err == nil, err
}

func updateReferences(st storage.Storer, req *packp.UpdateRequests, cmdStatus map[plumbing.ReferenceName]error, firstErr *error) {
        for _, cmd := range req.Commands {
                exists, err := referenceExists(st, cmd.Name)
                if err != nil {
                        setStatus(cmdStatus, firstErr, cmd.Name, err)
                        continue
                }

                switch cmd.Action() {
                case packp.Create:
                        if exists {
                                setStatus(cmdStatus, firstErr, cmd.Name, ErrUpdateReference)
                                continue
                        }

                        ref := plumbing.NewHashReference(cmd.Name, cmd.New)
                        err := st.SetReference(ref)
                        setStatus(cmdStatus, firstErr, cmd.Name, err)
                case packp.Delete:
                        if !exists {
                                setStatus(cmdStatus, firstErr, cmd.Name, ErrUpdateReference)
                                continue
                        }

                        err := st.RemoveReference(cmd.Name)
                        setStatus(cmdStatus, firstErr, cmd.Name, err)
                case packp.Update:
                        if !exists {
                                setStatus(cmdStatus, firstErr, cmd.Name, ErrUpdateReference)
                                continue
                        }

                        ref := plumbing.NewHashReference(cmd.Name, cmd.New)
                        err := st.SetReference(ref)
                        setStatus(cmdStatus, firstErr, cmd.Name, err)
                }
        }
}

package transport

import (
        "fmt"
        "sync"
)

// registry are the protocols supported by default.
var (
        registry = map[string]Transport{}
        mtx      sync.RWMutex
)

// Register adds or modifies an existing protocol.
// Equivalent to client.InstallProtocol in go-git before V6.
func Register(protocol string, c Transport) {
        mtx.Lock()
        registry[protocol] = c
        mtx.Unlock()
}

// Unregister removes a protocol from the list of supported protocols.
func Unregister(scheme string) {
        mtx.Lock()
        delete(registry, scheme)
        mtx.Unlock()
}

// Get returns the appropriate client for the given protocol.
func Get(p string) (Transport, error) {
        mtx.RLock()
        defer mtx.RUnlock()
        f, ok := registry[p]
        if !ok {
                return nil, fmt.Errorf("unsupported scheme %q", p)
        }

        if f == nil {
                return nil, fmt.Errorf("malformed client for scheme %q, client is defined as nil", p)
        }
        return f, nil
}

package transport

import (
        "context"
        "errors"
        "fmt"
        "io"

        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/object"
        "github.com/go-git/go-git/v6/plumbing/protocol/packp"
        "github.com/go-git/go-git/v6/plumbing/protocol/packp/capability"
        "github.com/go-git/go-git/v6/plumbing/storer"
        "github.com/go-git/go-git/v6/storage"
)

var ErrUpdateReference = errors.New("failed to update ref")

// AdvertiseReferences is a server command that implements the reference
// discovery phase of the Git transfer protocol.
func AdvertiseReferences(
        ctx context.Context,
        st storage.Storer,
        w io.Writer,
        service Service,
        smart bool,
) error {
        switch service {
        case UploadPackService, ReceivePackService:
        default:
                return fmt.Errorf("%w: %s", ErrUnsupportedService, service)
        }

        forPush := service == ReceivePackService
        ar := packp.NewAdvRefs()

        // Set server default capabilities
        ar.Capabilities.Set(capability.Agent, capability.DefaultAgent()) //nolint:errcheck
        ar.Capabilities.Set(capability.OFSDelta)                         //nolint:errcheck
        ar.Capabilities.Set(capability.Sideband64k)                      //nolint:errcheck
        if forPush {
                // TODO: support thin-pack
                ar.Capabilities.Set(capability.NoThin) //nolint:errcheck
                // TODO: support atomic
                ar.Capabilities.Set(capability.DeleteRefs)   //nolint:errcheck
                ar.Capabilities.Set(capability.ReportStatus) //nolint:errcheck
                ar.Capabilities.Set(capability.PushOptions)  //nolint:errcheck
        } else {
                // TODO: support include-tag
                // TODO: support deepen
                // TODO: support deepen-since
                ar.Capabilities.Set(capability.MultiACK)         //nolint:errcheck
                ar.Capabilities.Set(capability.MultiACKDetailed) //nolint:errcheck
                ar.Capabilities.Set(capability.Sideband)         //nolint:errcheck
                ar.Capabilities.Set(capability.NoProgress)       //nolint:errcheck
                ar.Capabilities.Set(capability.SymRef)           //nolint:errcheck
                ar.Capabilities.Set(capability.Shallow)          //nolint:errcheck
        }

        // Set references
        if err := addReferences(st, ar, !forPush); err != nil {
                return err
        }

        if smart {
                smartReply := packp.SmartReply{
                        Service: service.String(),
                }

                if err := smartReply.Encode(w); err != nil {
                        return fmt.Errorf("failed to encode smart reply: %w", err)
                }
        }

        return ar.Encode(w)
}

func addReferences(st storage.Storer, ar *packp.AdvRefs, addHead bool) error {
        iter, err := st.IterReferences()
        if err != nil {
                return err
        }

        // Add references and their peeled values
        if err := iter.ForEach(func(r *plumbing.Reference) error {
                hash, name := r.Hash(), r.Name()
                switch r.Type() {
                case plumbing.SymbolicReference:
                        ref, err := storer.ResolveReference(st, r.Target())
                        if errors.Is(err, plumbing.ErrReferenceNotFound) {
                                return nil
                        }
                        if err != nil {
                                return err
                        }
                        hash = ref.Hash()
                }
                if name == plumbing.HEAD {
                        if !addHead {
                                return nil
                        }
                        // Add default branch HEAD symref
                        ar.Capabilities.Add(capability.SymRef, fmt.Sprintf("%s:%s", name, r.Target())) //nolint:errcheck
                        ar.Head = &hash
                }
                ar.References[name.String()] = hash
                if r.Name().IsTag() {
                        if tag, err := object.GetTag(st, hash); err == nil {
                                ar.Peeled[name.String()] = tag.Target
                        }
                }
                return nil
        }); err != nil {
                return err
        }

        return nil
}

package transport

import (
        "fmt"

        "github.com/go-git/go-billy/v5"
        "github.com/go-git/go-git/v6/internal/repository"
        "github.com/go-git/go-git/v6/plumbing/storer"
        "github.com/go-git/go-git/v6/storage"
)

// UpdateServerInfo updates the server info files in the repository.
//
// It generates a list of available refs for the repository.
// Used by git http transport (dumb), for more information refer to:
// https://git-scm.com/book/id/v2/Git-Internals-Transfer-Protocols#_the_dumb_protocol
func UpdateServerInfo(s storage.Storer, fs billy.Filesystem) error {
        pos, ok := s.(storer.PackedObjectStorer)
        if !ok {
                return ErrPackedObjectsNotSupported
        }

        infoRefs, err := fs.Create("info/refs")
        if err != nil {
                return err
        }

        defer infoRefs.Close() //nolint:errcheck

        refsIter, err := s.IterReferences()
        if err != nil {
                return err
        }

        defer refsIter.Close()

        if err := repository.WriteInfoRefs(infoRefs, s); err != nil {
                return fmt.Errorf("failed to write info/refs: %w", err)
        }

        infoPacks, err := fs.Create("objects/info/packs")
        if err != nil {
                return err
        }

        defer infoPacks.Close() //nolint:errcheck

        if err := repository.WriteObjectsInfoPacks(infoPacks, pos); err != nil {
                return fmt.Errorf("failed to write objects/info/packs: %w", err)
        }

        return nil
}

package transport

import "strings"

// Service represents a Git transport service.
// All services are prefixed with "git-".
type Service string

// String returns the string representation of the service.
func (s Service) String() string {
        return string(s)
}

// Name returns the name of the service without the "git-" prefix.
func (s Service) Name() string {
        return strings.TrimPrefix(string(s), "git-")
}

// Git service names.
const (
        UploadPackService    Service = "git-upload-pack"
        UploadArchiveService Service = "git-upload-archive"
        ReceivePackService   Service = "git-receive-pack"
)

// Package transport includes the implementation for different transport
// protocols.
//
// `Client` can be used to fetch and send packfiles to a git server.
// The `client` package provides higher level functions to instantiate the
// appropriate `Client` based on the repository URL.
//
// go-git supports HTTP and SSH (see `Protocols`), but you can also install
// your own protocols (see the `client` package).
//
// Each protocol has its own implementation of `Client`, but you should
// generally not use them directly, use `client.NewClient` instead.
package transport

import (
        "bytes"
        "errors"
        "fmt"
        "net/url"
        "regexp"
        "runtime"
        "strconv"
        "strings"

        giturl "github.com/go-git/go-git/v6/internal/url"
        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/protocol"
        "github.com/go-git/go-git/v6/storage"
)

var (
        ErrRepositoryNotFound     = errors.New("repository not found")
        ErrEmptyRemoteRepository  = errors.New("remote repository is empty")
        ErrNoChange               = errors.New("no change")
        ErrAuthenticationRequired = errors.New("authentication required")
        ErrAuthorizationFailed    = errors.New("authorization failed")
        ErrEmptyUploadPackRequest = errors.New("empty git-upload-pack given")
        ErrInvalidAuthMethod      = errors.New("invalid auth method")
        ErrAlreadyConnected       = errors.New("session already established")
)

// Transport can initiate git-upload-pack and git-receive-pack processes.
// It is implemented both by the client and the server, making this a RPC.
type Transport interface {
        // NewSession returns a new session for an endpoint.
        NewSession(storage.Storer, *Endpoint, AuthMethod) (Session, error)

        // SupportedProtocols returns a list of supported Git protocol versions by
        // the transport client.
        SupportedProtocols() []protocol.Version
}

type AuthMethod interface {
        fmt.Stringer
        Name() string
}

// Endpoint represents a Git URL in any supported protocol.
type Endpoint struct {
        // Protocol is the protocol of the endpoint (e.g. git, https, file).
        Protocol string
        // User is the user.
        User string
        // Password is the password.
        Password string
        // Host is the host.
        Host string
        // Port is the port to connect, if 0 the default port for the given protocol
        // will be used.
        Port int
        // Path is the repository path.
        Path string
        // InsecureSkipTLS skips ssl verify if protocol is https
        InsecureSkipTLS bool
        // CaBundle specify additional ca bundle with system cert pool
        CaBundle []byte
        // Proxy provides info required for connecting to a proxy.
        Proxy ProxyOptions
}

type ProxyOptions struct {
        URL      string
        Username string
        Password string
}

func (o *ProxyOptions) Validate() error {
        if o.URL != "" {
                _, err := url.Parse(o.URL)
                return err
        }
        return nil
}

func (o *ProxyOptions) FullURL() (*url.URL, error) {
        proxyURL, err := url.Parse(o.URL)
        if err != nil {
                return nil, err
        }
        if o.Username != "" {
                if o.Password != "" {
                        proxyURL.User = url.UserPassword(o.Username, o.Password)
                } else {
                        proxyURL.User = url.User(o.Username)
                }
        }
        return proxyURL, nil
}

var defaultPorts = map[string]int{
        "http":  80,
        "https": 443,
        "git":   9418,
        "ssh":   22,
}

var fileIssueWindows = regexp.MustCompile(`^/[A-Za-z]:(/|\\)`)

// String returns a string representation of the Git URL.
func (u *Endpoint) String() string {
        var buf bytes.Buffer
        if u.Protocol != "" {
                buf.WriteString(u.Protocol)
                buf.WriteByte(':')
        }

        if u.Protocol != "" || u.Host != "" || u.User != "" || u.Password != "" {
                buf.WriteString("//")

                if u.User != "" || u.Password != "" {
                        buf.WriteString(url.PathEscape(u.User))
                        if u.Password != "" {
                                buf.WriteByte(':')
                                buf.WriteString(url.PathEscape(u.Password))
                        }

                        buf.WriteByte('@')
                }

                if u.Host != "" {
                        buf.WriteString(u.Host)

                        if u.Port != 0 {
                                port, ok := defaultPorts[strings.ToLower(u.Protocol)]
                                if !ok || ok && port != u.Port {
                                        fmt.Fprintf(&buf, ":%d", u.Port)
                                }
                        }
                }
        }

        if u.Path != "" && u.Path[0] != '/' && u.Host != "" {
                buf.WriteByte('/')
        }

        buf.WriteString(u.Path)
        return buf.String()
}

func NewEndpoint(endpoint string) (*Endpoint, error) {
        if e, ok := parseSCPLike(endpoint); ok {
                return e, nil
        }

        if e, ok := parseFile(endpoint); ok {
                return e, nil
        }

        return parseURL(endpoint)
}

func parseURL(endpoint string) (*Endpoint, error) {
        if strings.HasPrefix(endpoint, "file://") {
                endpoint = strings.TrimPrefix(endpoint, "file://")

                // When triple / is used, the path in Windows may end up having an
                // additional / resulting in "/C:/Dir".
                if runtime.GOOS == "windows" &&
                        fileIssueWindows.MatchString(endpoint) {
                        endpoint = endpoint[1:]
                }
                return &Endpoint{
                        Protocol: "file",
                        Path:     endpoint,
                }, nil
        }

        u, err := url.Parse(endpoint)
        if err != nil {
                return nil, err
        }

        if !u.IsAbs() {
                return nil, plumbing.NewPermanentError(fmt.Errorf(
                        "invalid endpoint: %s", endpoint,
                ))
        }

        var user, pass string
        if u.User != nil {
                user = u.User.Username()
                pass, _ = u.User.Password()
        }

        host := u.Hostname()
        if strings.Contains(host, ":") {
                // IPv6 address
                host = "[" + host + "]"
        }

        return &Endpoint{
                Protocol: u.Scheme,
                User:     user,
                Password: pass,
                Host:     host,
                Port:     getPort(u),
                Path:     getPath(u),
        }, nil
}

func getPort(u *url.URL) int {
        p := u.Port()
        if p == "" {
                return 0
        }

        i, err := strconv.Atoi(p)
        if err != nil {
                return 0
        }

        return i
}

func getPath(u *url.URL) string {
        var res string = u.Path
        if u.RawQuery != "" {
                res += "?" + u.RawQuery
        }

        if u.Fragment != "" {
                res += "#" + u.Fragment
        }

        return res
}

func parseSCPLike(endpoint string) (*Endpoint, bool) {
        if giturl.MatchesScheme(endpoint) || !giturl.MatchesScpLike(endpoint) {
                return nil, false
        }

        user, host, portStr, path := giturl.FindScpLikeComponents(endpoint)
        port, err := strconv.Atoi(portStr)
        if err != nil {
                port = 22
        }

        return &Endpoint{
                Protocol: "ssh",
                User:     user,
                Host:     host,
                Port:     port,
                Path:     path,
        }, true
}

func parseFile(endpoint string) (*Endpoint, bool) {
        if giturl.MatchesScheme(endpoint) {
                return nil, false
        }

        path := endpoint
        return &Endpoint{
                Protocol: "file",
                Path:     path,
        }, true
}

package transport

import (
        "bufio"
        "context"
        "fmt"
        "io"
        "math"

        "github.com/go-git/go-git/v6/plumbing"
        "github.com/go-git/go-git/v6/plumbing/format/packfile"
        "github.com/go-git/go-git/v6/plumbing/format/pktline"
        "github.com/go-git/go-git/v6/plumbing/object"
        "github.com/go-git/go-git/v6/plumbing/protocol"
        "github.com/go-git/go-git/v6/plumbing/protocol/packp"
        "github.com/go-git/go-git/v6/plumbing/protocol/packp/capability"
        "github.com/go-git/go-git/v6/plumbing/protocol/packp/sideband"
        "github.com/go-git/go-git/v6/plumbing/revlist"
        "github.com/go-git/go-git/v6/storage"
        "github.com/go-git/go-git/v6/utils/ioutil"
)

// UploadPackOptions is a set of options for the UploadPack service.
type UploadPackOptions struct {
        GitProtocol   string
        AdvertiseRefs bool
        StatelessRPC  bool
}

// UploadPack is a server command that serves the upload-pack service.
func UploadPack(
        ctx context.Context,
        st storage.Storer,
        r io.ReadCloser,
        w io.WriteCloser,
        opts *UploadPackOptions,
) error {
        if w == nil {
                return fmt.Errorf("nil writer")
        }

        w = ioutil.NewContextWriteCloser(ctx, w)

        if opts == nil {
                opts = &UploadPackOptions{}
        }

        if opts.AdvertiseRefs || !opts.StatelessRPC {
                switch version := ProtocolVersion(opts.GitProtocol); version {
                case protocol.V1:
                        if _, err := pktline.Writef(w, "version %d\n", version); err != nil {
                                return err
                        }
                // TODO: support version 2
                case protocol.V0, protocol.V2:
                default:
                        return fmt.Errorf("%w: %q", ErrUnsupportedVersion, version)
                }

                if err := AdvertiseReferences(ctx, st, w, UploadPackService, opts.StatelessRPC); err != nil {
                        return fmt.Errorf("advertising references: %w", err)
                }
        }

        if opts.AdvertiseRefs {
                // Done, there's nothing else to do
                return nil
        }

        if r == nil {
                return fmt.Errorf("nil reader")
        }

        r = ioutil.NewContextReadCloser(ctx, r)

        rd := bufio.NewReader(r)
        l, _, err := pktline.PeekLine(rd)
        if err != nil {
                return fmt.Errorf("peeking line: %w", err)
        }

        // In case the client has nothing to send, it sends a flush packet to
        // indicate that it is done sending data. In that case, we're done
        // here.
        if l == pktline.Flush {
                return nil
        }

        var done bool
        var haves []plumbing.Hash
        var upreq *packp.UploadRequest
        var havesWithRef map[plumbing.Hash][]plumbing.Hash
        var multiAck, multiAckDetailed bool
        var caps *capability.List
        var wants []plumbing.Hash
        firstRound := true
        for !done {
                writec := make(chan error)
                if firstRound || opts.StatelessRPC {
                        upreq = packp.NewUploadRequest()
                        if err := upreq.Decode(rd); err != nil {
                                return fmt.Errorf("decoding upload-request: %w", err)
                        }

                        wants = upreq.Wants
                        caps = upreq.Capabilities

                        if err := r.Close(); err != nil {
                                return fmt.Errorf("closing reader: %w", err)
                        }

                        // Find common commits/objects
                        havesWithRef, err = revlist.ObjectsWithRef(st, wants, nil)
                        if err != nil {
                                return fmt.Errorf("getting objects with ref: %w", err)
                        }

                        // Encode objects to packfile and write to client
                        multiAck = caps.Supports(capability.MultiACK)
                        multiAckDetailed = caps.Supports(capability.MultiACKDetailed)

                        go func() {
                                // TODO: support deepen-since, and deepen-not
                                var shupd packp.ShallowUpdate
                                if !upreq.Depth.IsZero() {
                                        switch depth := upreq.Depth.(type) {
                                        case packp.DepthCommits:
                                                if err := getShallowCommits(st, wants, int(depth), &shupd); err != nil {
                                                        writec <- fmt.Errorf("getting shallow commits: %w", err)
                                                        return
                                                }
                                        default:
                                                writec <- fmt.Errorf("unsupported depth type %T", upreq.Depth)
                                                return
                                        }

                                        if err := shupd.Encode(w); err != nil {
                                                writec <- fmt.Errorf("sending shallow-update: %w", err)
                                                return
                                        }
                                }

                                writec <- nil
                        }()
                }

                if err := <-writec; err != nil {
                        return err
                }

                var uphav packp.UploadHaves
                if err := uphav.Decode(rd); err != nil {
                        return fmt.Errorf("decoding upload-haves: %w", err)
                }

                if err := r.Close(); err != nil {
                        return fmt.Errorf("closing reader: %w", err)
                }

                haves = append(haves, uphav.Haves...)
                done = uphav.Done

                common := map[plumbing.Hash]struct{}{}
                var ack packp.ACK
                var acks []packp.ACK
                for _, hu := range uphav.Haves {
                        refs, ok := havesWithRef[hu]
                        if ok {
                                for _, ref := range refs {
                                        common[ref] = struct{}{}
                                }
                        }

                        var status packp.ACKStatus
                        if multiAckDetailed {
                                status = packp.ACKCommon
                                if !ok {
                                        status = packp.ACKReady
                                }
                        } else if multiAck {
                                status = packp.ACKContinue
                        }

                        if ok || multiAck || multiAckDetailed {
                                ack = packp.ACK{Hash: hu, Status: status}
                                acks = append(acks, ack)
                                if !multiAck && !multiAckDetailed {
                                        break
                                }
                        }
                }

                go func() {
                        defer close(writec)

                        if len(haves) > 0 {
                                // Encode ACKs to client when we have haves
                                srvrsp := packp.ServerResponse{ACKs: acks}
                                if err := srvrsp.Encode(w); err != nil {
                                        writec <- fmt.Errorf("sending acks server-response: %w", err)
                                        return
                                }
                        }

                        if !done {
                                if multiAck || multiAckDetailed {
                                        // Encode a NAK for multi-ack
                                        srvrsp := packp.ServerResponse{}
                                        if err := srvrsp.Encode(w); err != nil {
                                                writec <- fmt.Errorf("sending nak server-response: %w", err)
                                                return
                                        }
                                }
                        } else if !ack.Hash.IsZero() && (multiAck || multiAckDetailed) {
                                // We're done, send the final ACK
                                ack.Status = 0
                                srvrsp := packp.ServerResponse{ACKs: []packp.ACK{ack}}
                                if err := srvrsp.Encode(w); err != nil {
                                        writec <- fmt.Errorf("sending final ack server-response: %w", err)
                                        return
                                }
                        } else if ack.Hash.IsZero() {
                                // We don't have multi-ack and there are no haves. Encode a NAK.
                                srvrsp := packp.ServerResponse{}
                                if err := srvrsp.Encode(w); err != nil {
                                        writec <- fmt.Errorf("sending final nak server-response: %w", err)
                                        return
                                }
                        }

                        writec <- nil
                }()

                if err := <-writec; err != nil {
                        return err
                }

                firstRound = false
        }

        // Done with the request, now close the reader
        // to indicate that we are done reading from it.
        if err := r.Close(); err != nil {
                return fmt.Errorf("closing reader: %w", err)
        }

        objs, err := objectsToUpload(st, wants, haves)
        if err != nil {
                w.Close() //nolint:errcheck
                return fmt.Errorf("getting objects to upload: %w", err)
        }

        var (
                useSideband bool
                writer      io.Writer = w
        )
        if !caps.Supports(capability.NoProgress) {
                if caps.Supports(capability.Sideband64k) {
                        writer = sideband.NewMuxer(sideband.Sideband64k, w)
                        useSideband = true
                } else if caps.Supports(capability.Sideband) {
                        writer = sideband.NewMuxer(sideband.Sideband, w)
                        useSideband = true
                }
        }

        // TODO: Support shallow-file
        // TODO: Support thin-pack
        e := packfile.NewEncoder(writer, st, false)
        _, err = e.Encode(objs, 10)
        if err != nil {
                return fmt.Errorf("encoding packfile: %w", err)
        }

        if useSideband {
                if err := pktline.WriteFlush(w); err != nil {
                        return fmt.Errorf("flushing sideband: %w", err)
                }
        }

        if err := w.Close(); err != nil {
                return fmt.Errorf("closing writer: %w", err)
        }

        return nil
}

func objectsToUpload(st storage.Storer, wants, haves []plumbing.Hash) ([]plumbing.Hash, error) {
        return revlist.Objects(st, wants, haves)
}

func getShallowCommits(st storage.Storer, heads []plumbing.Hash, depth int, upd *packp.ShallowUpdate) error {
        var i, curDepth int
        var commit *object.Commit
        depths := map[*object.Commit]int{}
        stack := []object.Object{}

        for commit != nil || i < len(heads) || len(stack) > 0 {
                if commit == nil {
                        if i < len(heads) {
                                obj, err := st.EncodedObject(plumbing.CommitObject, heads[i])
                                i++
                                if err != nil {
                                        continue
                                }

                                commit, err = object.DecodeCommit(st, obj)
                                if err != nil {
                                        commit = nil
                                        continue
                                }

                                depths[commit] = 0
                                curDepth = 0
                        } else if len(stack) > 0 {
                                commit = stack[len(stack)-1].(*object.Commit)
                                stack = stack[:len(stack)-1]
                                curDepth = depths[commit]
                        }
                }

                curDepth++

                if depth != math.MaxInt && curDepth >= depth {
                        upd.Shallows = append(upd.Shallows, commit.Hash)
                        commit = nil
                        continue
                }

                upd.Unshallows = append(upd.Unshallows, commit.Hash)

                parents := commit.Parents()
                commit = nil
                for {
                        parent, err := parents.Next()
                        if err == io.EOF {
                                break
                        }
                        if err != nil {
                                return err
                        }

                        if depths[parent] != 0 && curDepth >= depths[parent] {
                                continue
                        }

                        depths[parent] = curDepth

                        if _, err := parents.Next(); err == nil {
                                stack = append(stack, parent)
                        } else {
                                commit = parent
                                curDepth = depths[commit]
                        }
                }

        }

        return nil
}

package transport

import (
        "strings"

        "github.com/go-git/go-git/v6/plumbing/format/pktline"
        "github.com/go-git/go-git/v6/plumbing/protocol"
        "github.com/go-git/go-git/v6/utils/ioutil"
)

// DiscoverVersion reads the first pktline from the reader to determine the
// protocol version. This is used by the client to determine the protocol
// version of the server.
func DiscoverVersion(r ioutil.ReadPeeker) (protocol.Version, error) {
        ver := protocol.V0
        _, pktb, err := pktline.PeekLine(r)
        if err != nil {
                return ver, err
        }

        pkt := strings.TrimSpace(string(pktb))
        if strings.HasPrefix(pkt, "version ") {
                // Consume the version packet
                pktline.ReadLine(r) // nolint:errcheck
                if v, _ := protocol.Parse(pkt[8:]); v > ver {
                        ver = protocol.Version(v)
                }
        }

        return ver, nil
}

// ProtocolVersion tries to find the version parameter in the protocol string.
// This expects the protocol string from the GIT_PROTOCOL environment variable.
// This is used by the server to determine the protocol version requested by
// the client.
func ProtocolVersion(p string) protocol.Version {
        var ver protocol.Version
        for _, param := range strings.Split(p, ":") {
                if strings.HasPrefix(param, "version=") {
                        if v, _ := protocol.Parse(param[8:]); v > ver {
                                ver = protocol.Version(v)
                        }
                }
        }
        return ver
}