/src/git/diff.c

Source
/*
 * Copyright (C) 2005 Junio C Hamano
 */

#define USE_THE_REPOSITORY_VARIABLE
#define DISABLE_SIGN_COMPARE_WARNINGS

#include "git-compat-util.h"
#include "abspath.h"
#include "base85.h"
#include "config.h"
#include "convert.h"
#include "environment.h"
#include "gettext.h"
#include "tempfile.h"
#include "revision.h"
#include "quote.h"
#include "diff.h"
#include "diffcore.h"
#include "delta.h"
#include "hex.h"
#include "xdiff-interface.h"
#include "color.h"
#include "run-command.h"
#include "utf8.h"
#include "odb.h"
#include "userdiff.h"
#include "submodule.h"
#include "hashmap.h"
#include "mem-pool.h"
#include "merge-ll.h"
#include "string-list.h"
#include "strvec.h"
#include "tmp-objdir.h"
#include "graph.h"
#include "oid-array.h"
#include "packfile.h"
#include "pager.h"
#include "parse-options.h"
#include "help.h"
#include "promisor-remote.h"
#include "dir.h"
#include "object-file.h"
#include "object-name.h"
#include "read-cache-ll.h"
#include "setup.h"
#include "strmap.h"
#include "ws.h"

#ifdef NO_FAST_WORKING_DIRECTORY
#define FAST_WORKING_DIRECTORY 0
#else
#define FAST_WORKING_DIRECTORY 1
#endif

static int diff_detect_rename_default;
static int diff_indent_heuristic = 1;
static int diff_rename_limit_default = 1000;
static int diff_suppress_blank_empty;
static enum git_colorbool diff_use_color_default = GIT_COLOR_UNKNOWN;
static int diff_color_moved_default;
static int diff_color_moved_ws_default;
static unsigned int diff_context_default = 3;
static unsigned int diff_interhunk_context_default;
static char *diff_word_regex_cfg;
static struct external_diff external_diff_cfg;
static char *diff_order_file_cfg;
int diff_auto_refresh_index = 1;
static int diff_mnemonic_prefix;
static int diff_no_prefix;
static char *diff_src_prefix;
static char *diff_dst_prefix;
static int diff_relative;
static int diff_stat_name_width;
static int diff_stat_graph_width;
static int diff_dirstat_permille_default = 30;
static struct diff_options default_diff_options;
static long diff_algorithm;
static unsigned ws_error_highlight_default = WSEH_NEW;

static char diff_colors[][COLOR_MAXLEN] = {
  GIT_COLOR_RESET,
  GIT_COLOR_NORMAL, /* CONTEXT */
  GIT_COLOR_BOLD,   /* METAINFO */
  GIT_COLOR_CYAN,   /* FRAGINFO */
  GIT_COLOR_RED,    /* OLD */
  GIT_COLOR_GREEN,  /* NEW */
  GIT_COLOR_YELLOW, /* COMMIT */
  GIT_COLOR_BG_RED, /* WHITESPACE */
  GIT_COLOR_NORMAL, /* FUNCINFO */
  GIT_COLOR_BOLD_MAGENTA, /* OLD_MOVED */
  GIT_COLOR_BOLD_BLUE,  /* OLD_MOVED ALTERNATIVE */
  GIT_COLOR_FAINT,  /* OLD_MOVED_DIM */
  GIT_COLOR_FAINT_ITALIC, /* OLD_MOVED_ALTERNATIVE_DIM */
  GIT_COLOR_BOLD_CYAN,  /* NEW_MOVED */
  GIT_COLOR_BOLD_YELLOW,  /* NEW_MOVED ALTERNATIVE */
  GIT_COLOR_FAINT,  /* NEW_MOVED_DIM */
  GIT_COLOR_FAINT_ITALIC, /* NEW_MOVED_ALTERNATIVE_DIM */
  GIT_COLOR_FAINT,  /* CONTEXT_DIM */
  GIT_COLOR_FAINT_RED,  /* OLD_DIM */
  GIT_COLOR_FAINT_GREEN,  /* NEW_DIM */
  GIT_COLOR_BOLD,   /* CONTEXT_BOLD */
  GIT_COLOR_BOLD_RED, /* OLD_BOLD */
  GIT_COLOR_BOLD_GREEN, /* NEW_BOLD */
};

static const char *color_diff_slots[] = {
  [DIFF_CONTEXT]          = "context",
  [DIFF_METAINFO]         = "meta",
  [DIFF_FRAGINFO]         = "frag",
  [DIFF_FILE_OLD]         = "old",
  [DIFF_FILE_NEW]         = "new",
  [DIFF_COMMIT]         = "commit",
  [DIFF_WHITESPACE]       = "whitespace",
  [DIFF_FUNCINFO]         = "func",
  [DIFF_FILE_OLD_MOVED]       = "oldMoved",
  [DIFF_FILE_OLD_MOVED_ALT]     = "oldMovedAlternative",
  [DIFF_FILE_OLD_MOVED_DIM]     = "oldMovedDimmed",
  [DIFF_FILE_OLD_MOVED_ALT_DIM] = "oldMovedAlternativeDimmed",
  [DIFF_FILE_NEW_MOVED]       = "newMoved",
  [DIFF_FILE_NEW_MOVED_ALT]     = "newMovedAlternative",
  [DIFF_FILE_NEW_MOVED_DIM]     = "newMovedDimmed",
  [DIFF_FILE_NEW_MOVED_ALT_DIM] = "newMovedAlternativeDimmed",
  [DIFF_CONTEXT_DIM]        = "contextDimmed",
  [DIFF_FILE_OLD_DIM]       = "oldDimmed",
  [DIFF_FILE_NEW_DIM]       = "newDimmed",
  [DIFF_CONTEXT_BOLD]       = "contextBold",
  [DIFF_FILE_OLD_BOLD]        = "oldBold",
  [DIFF_FILE_NEW_BOLD]        = "newBold",
};

define_list_config_array_extra(color_diff_slots, {"plain"});

static int parse_diff_color_slot(const char *var)
{
  if (!strcasecmp(var, "plain"))
    return DIFF_CONTEXT;
  return LOOKUP_CONFIG(color_diff_slots, var);
}

static int parse_dirstat_params(struct diff_options *options, const char *params_string,
        struct strbuf *errmsg)
{
  char *params_copy = xstrdup(params_string);
  struct string_list params = STRING_LIST_INIT_NODUP;
  int ret = 0;
  int i;

  if (*params_copy)
    string_list_split_in_place(&params, params_copy, ",", -1);
  for (i = 0; i < params.nr; i++) {
    const char *p = params.items[i].string;
    if (!strcmp(p, "changes")) {
      options->flags.dirstat_by_line = 0;
      options->flags.dirstat_by_file = 0;
    } else if (!strcmp(p, "lines")) {
      options->flags.dirstat_by_line = 1;
      options->flags.dirstat_by_file = 0;
    } else if (!strcmp(p, "files")) {
      options->flags.dirstat_by_line = 0;
      options->flags.dirstat_by_file = 1;
    } else if (!strcmp(p, "noncumulative")) {
      options->flags.dirstat_cumulative = 0;
    } else if (!strcmp(p, "cumulative")) {
      options->flags.dirstat_cumulative = 1;
    } else if (isdigit(*p)) {
      char *end;
      int permille = strtoul(p, &end, 10) * 10;
      if (*end == '.' && isdigit(*++end)) {
        /* only use first digit */
        permille += *end - '0';
        /* .. and ignore any further digits */
        while (isdigit(*++end))
          ; /* nothing */
      }
      if (!*end)
        options->dirstat_permille = permille;
      else {
        strbuf_addf(errmsg, _("  Failed to parse dirstat cut-off percentage '%s'\n"),
              p);
        ret++;
      }
    } else {
      strbuf_addf(errmsg, _("  Unknown dirstat parameter '%s'\n"), p);
      ret++;
    }

  }
  string_list_clear(&params, 0);
  free(params_copy);
  return ret;
}

static int parse_submodule_params(struct diff_options *options, const char *value)
{
  if (!strcmp(value, "log"))
    options->submodule_format = DIFF_SUBMODULE_LOG;
  else if (!strcmp(value, "short"))
    options->submodule_format = DIFF_SUBMODULE_SHORT;
  else if (!strcmp(value, "diff"))
    options->submodule_format = DIFF_SUBMODULE_INLINE_DIFF;
  /*
   * Please update $__git_diff_submodule_formats in
   * git-completion.bash when you add new formats.
   */
  else
    return -1;
  return 0;
}

int git_config_rename(const char *var, const char *value)
{
  if (!value)
    return DIFF_DETECT_RENAME;
  if (!strcasecmp(value, "copies") || !strcasecmp(value, "copy"))
    return  DIFF_DETECT_COPY;
  return git_config_bool(var,value) ? DIFF_DETECT_RENAME : 0;
}

long parse_algorithm_value(const char *value)
{
  if (!value)
    return -1;
  else if (!strcasecmp(value, "myers") || !strcasecmp(value, "default"))
    return 0;
  else if (!strcasecmp(value, "minimal"))
    return XDF_NEED_MINIMAL;
  else if (!strcasecmp(value, "patience"))
    return XDF_PATIENCE_DIFF;
  else if (!strcasecmp(value, "histogram"))
    return XDF_HISTOGRAM_DIFF;
  /*
   * Please update $__git_diff_algorithms in git-completion.bash
   * when you add new algorithms.
   */
  return -1;
}

static int parse_one_token(const char **arg, const char *token)
{
  const char *rest;
  if (skip_prefix(*arg, token, &rest) && (!*rest || *rest == ',')) {
    *arg = rest;
    return 1;
  }
  return 0;
}

static int parse_ws_error_highlight(const char *arg)
{
  const char *orig_arg = arg;
  unsigned val = 0;

  while (*arg) {
    if (parse_one_token(&arg, "none"))
      val = 0;
    else if (parse_one_token(&arg, "default"))
      val = WSEH_NEW;
    else if (parse_one_token(&arg, "all"))
      val = WSEH_NEW | WSEH_OLD | WSEH_CONTEXT;
    else if (parse_one_token(&arg, "new"))
      val |= WSEH_NEW;
    else if (parse_one_token(&arg, "old"))
      val |= WSEH_OLD;
    else if (parse_one_token(&arg, "context"))
      val |= WSEH_CONTEXT;
    else {
      return -1 - (int)(arg - orig_arg);
    }
    if (*arg)
      arg++;
  }
  return val;
}

/*
 * These are to give UI layer defaults.
 * The core-level commands such as git-diff-files should
 * never be affected by the setting of diff.renames
 * the user happens to have in the configuration file.
 */
void init_diff_ui_defaults(void)
{
  diff_detect_rename_default = DIFF_DETECT_RENAME;
}

int git_diff_heuristic_config(const char *var, const char *value,
            void *cb UNUSED)
{
  if (!strcmp(var, "diff.indentheuristic"))
    diff_indent_heuristic = git_config_bool(var, value);
  return 0;
}

static int parse_color_moved(const char *arg)
{
  switch (git_parse_maybe_bool(arg)) {
  case 0:
    return COLOR_MOVED_NO;
  case 1:
    return COLOR_MOVED_DEFAULT;
  default:
    break;
  }

  if (!strcmp(arg, "no"))
    return COLOR_MOVED_NO;
  else if (!strcmp(arg, "plain"))
    return COLOR_MOVED_PLAIN;
  else if (!strcmp(arg, "blocks"))
    return COLOR_MOVED_BLOCKS;
  else if (!strcmp(arg, "zebra"))
    return COLOR_MOVED_ZEBRA;
  else if (!strcmp(arg, "default"))
    return COLOR_MOVED_DEFAULT;
  else if (!strcmp(arg, "dimmed-zebra"))
    return COLOR_MOVED_ZEBRA_DIM;
  else if (!strcmp(arg, "dimmed_zebra"))
    return COLOR_MOVED_ZEBRA_DIM;
  else
    return error(_("color moved setting must be one of 'no', 'default', 'blocks', 'zebra', 'dimmed-zebra', 'plain'"));
}

static unsigned parse_color_moved_ws(const char *arg)
{
  int ret = 0;
  struct string_list l = STRING_LIST_INIT_DUP;
  struct string_list_item *i;

  string_list_split_f(&l, arg, ",", -1, STRING_LIST_SPLIT_TRIM);

  for_each_string_list_item(i, &l) {
    if (!strcmp(i->string, "no"))
      ret = 0;
    else if (!strcmp(i->string, "ignore-space-change"))
      ret |= XDF_IGNORE_WHITESPACE_CHANGE;
    else if (!strcmp(i->string, "ignore-space-at-eol"))
      ret |= XDF_IGNORE_WHITESPACE_AT_EOL;
    else if (!strcmp(i->string, "ignore-all-space"))
      ret |= XDF_IGNORE_WHITESPACE;
    else if (!strcmp(i->string, "allow-indentation-change"))
      ret |= COLOR_MOVED_WS_ALLOW_INDENTATION_CHANGE;
    else {
      ret |= COLOR_MOVED_WS_ERROR;
      error(_("unknown color-moved-ws mode '%s', possible values are 'ignore-space-change', 'ignore-space-at-eol', 'ignore-all-space', 'allow-indentation-change'"), i->string);
    }
  }

  if ((ret & COLOR_MOVED_WS_ALLOW_INDENTATION_CHANGE) &&
      (ret & XDF_WHITESPACE_FLAGS)) {
    error(_("color-moved-ws: allow-indentation-change cannot be combined with other whitespace modes"));
    ret |= COLOR_MOVED_WS_ERROR;
  }

  string_list_clear(&l, 0);

  return ret;
}

int git_diff_ui_config(const char *var, const char *value,
           const struct config_context *ctx, void *cb)
{
  if (!strcmp(var, "diff.color") || !strcmp(var, "color.diff")) {
    diff_use_color_default = git_config_colorbool(var, value);
    return 0;
  }
  if (!strcmp(var, "diff.colormoved")) {
    int cm = parse_color_moved(value);
    if (cm < 0)
      return -1;
    diff_color_moved_default = cm;
    return 0;
  }
  if (!strcmp(var, "diff.colormovedws")) {
    unsigned cm;
    if (!value)
      return config_error_nonbool(var);
    cm = parse_color_moved_ws(value);
    if (cm & COLOR_MOVED_WS_ERROR)
      return -1;
    diff_color_moved_ws_default = cm;
    return 0;
  }
  if (!strcmp(var, "diff.context")) {
    int val = git_config_int(var, value, ctx->kvi);
    if (val < 0)
      return -1;
    diff_context_default = val;
    return 0;
  }
  if (!strcmp(var, "diff.interhunkcontext")) {
    int val = git_config_int(var, value, ctx->kvi);
    if (val < 0)
      return -1;
    diff_interhunk_context_default = val;
    return 0;
  }
  if (!strcmp(var, "diff.renames")) {
    diff_detect_rename_default = git_config_rename(var, value);
    return 0;
  }
  if (!strcmp(var, "diff.autorefreshindex")) {
    diff_auto_refresh_index = git_config_bool(var, value);
    return 0;
  }
  if (!strcmp(var, "diff.mnemonicprefix")) {
    diff_mnemonic_prefix = git_config_bool(var, value);
    return 0;
  }
  if (!strcmp(var, "diff.noprefix")) {
    diff_no_prefix = git_config_bool(var, value);
    return 0;
  }
  if (!strcmp(var, "diff.srcprefix")) {
    FREE_AND_NULL(diff_src_prefix);
    return git_config_string(&diff_src_prefix, var, value);
  }
  if (!strcmp(var, "diff.dstprefix")) {
    FREE_AND_NULL(diff_dst_prefix);
    return git_config_string(&diff_dst_prefix, var, value);
  }
  if (!strcmp(var, "diff.relative")) {
    diff_relative = git_config_bool(var, value);
    return 0;
  }
  if (!strcmp(var, "diff.statnamewidth")) {
    diff_stat_name_width = git_config_int(var, value, ctx->kvi);
    return 0;
  }
  if (!strcmp(var, "diff.statgraphwidth")) {
    diff_stat_graph_width = git_config_int(var, value, ctx->kvi);
    return 0;
  }
  if (!strcmp(var, "diff.external"))
    return git_config_string(&external_diff_cfg.cmd, var, value);
  if (!strcmp(var, "diff.trustexitcode")) {
    external_diff_cfg.trust_exit_code = git_config_bool(var, value);
    return 0;
  }
  if (!strcmp(var, "diff.wordregex"))
    return git_config_string(&diff_word_regex_cfg, var, value);
  if (!strcmp(var, "diff.orderfile")) {
    FREE_AND_NULL(diff_order_file_cfg);
    return git_config_pathname(&diff_order_file_cfg, var, value);
  }

  if (!strcmp(var, "diff.ignoresubmodules")) {
    if (!value)
      return config_error_nonbool(var);
    handle_ignore_submodules_arg(&default_diff_options, value);
  }

  if (!strcmp(var, "diff.submodule")) {
    if (!value)
      return config_error_nonbool(var);
    if (parse_submodule_params(&default_diff_options, value))
      warning(_("Unknown value for 'diff.submodule' config variable: '%s'"),
        value);
    return 0;
  }

  if (!strcmp(var, "diff.algorithm")) {
    if (!value)
      return config_error_nonbool(var);
    diff_algorithm = parse_algorithm_value(value);
    if (diff_algorithm < 0)
      return error(_("unknown value for config '%s': %s"),
             var, value);
    return 0;
  }

  if (git_color_config(var, value, cb) < 0)
    return -1;

  return git_diff_basic_config(var, value, ctx, cb);
}

int git_diff_basic_config(const char *var, const char *value,
        const struct config_context *ctx, void *cb)
{
  const char *name;

  if (!strcmp(var, "diff.renamelimit")) {
    diff_rename_limit_default = git_config_int(var, value, ctx->kvi);
    return 0;
  }

  if (userdiff_config(var, value) < 0)
    return -1;

  if (skip_prefix(var, "diff.color.", &name) ||
      skip_prefix(var, "color.diff.", &name)) {
    int slot = parse_diff_color_slot(name);
    if (slot < 0)
      return 0;
    if (!value)
      return config_error_nonbool(var);
    return color_parse(value, diff_colors[slot]);
  }

  if (!strcmp(var, "diff.wserrorhighlight")) {
    int val;
    if (!value)
      return config_error_nonbool(var);
    val = parse_ws_error_highlight(value);
    if (val < 0)
      return error(_("unknown value for config '%s': %s"),
             var, value);
    ws_error_highlight_default = val;
    return 0;
  }

  /* like GNU diff's --suppress-blank-empty option  */
  if (!strcmp(var, "diff.suppressblankempty") ||
      /* for backwards compatibility */
      !strcmp(var, "diff.suppress-blank-empty")) {
    diff_suppress_blank_empty = git_config_bool(var, value);
    return 0;
  }

  if (!strcmp(var, "diff.dirstat")) {
    struct strbuf errmsg = STRBUF_INIT;
    if (!value)
      return config_error_nonbool(var);
    default_diff_options.dirstat_permille = diff_dirstat_permille_default;
    if (parse_dirstat_params(&default_diff_options, value, &errmsg))
      warning(_("Found errors in 'diff.dirstat' config variable:\n%s"),
        errmsg.buf);
    strbuf_release(&errmsg);
    diff_dirstat_permille_default = default_diff_options.dirstat_permille;
    return 0;
  }

  if (git_diff_heuristic_config(var, value, cb) < 0)
    return -1;

  return git_default_config(var, value, ctx, cb);
}

static char *quote_two(const char *one, const char *two)
{
  int need_one = quote_c_style(one, NULL, NULL, CQUOTE_NODQ);
  int need_two = quote_c_style(two, NULL, NULL, CQUOTE_NODQ);
  struct strbuf res = STRBUF_INIT;

  if (need_one + need_two) {
    strbuf_addch(&res, '"');
    quote_c_style(one, &res, NULL, CQUOTE_NODQ);
    quote_c_style(two, &res, NULL, CQUOTE_NODQ);
    strbuf_addch(&res, '"');
  } else {
    strbuf_addstr(&res, one);
    strbuf_addstr(&res, two);
  }
  return strbuf_detach(&res, NULL);
}

static const struct external_diff *external_diff(void)
{
  static struct external_diff external_diff_env, *external_diff_ptr;
  static int done_preparing = 0;

  if (done_preparing)
    return external_diff_ptr;
  external_diff_env.cmd = xstrdup_or_null(getenv("GIT_EXTERNAL_DIFF"));
  if (git_env_bool("GIT_EXTERNAL_DIFF_TRUST_EXIT_CODE", 0))
    external_diff_env.trust_exit_code = 1;
  if (external_diff_env.cmd)
    external_diff_ptr = &external_diff_env;
  else if (external_diff_cfg.cmd)
    external_diff_ptr = &external_diff_cfg;
  done_preparing = 1;
  return external_diff_ptr;
}

/*
 * Keep track of files used for diffing. Sometimes such an entry
 * refers to a temporary file, sometimes to an existing file, and
 * sometimes to "/dev/null".
 */
static struct diff_tempfile {
  /*
   * filename external diff should read from, or NULL if this
   * entry is currently not in use:
   */
  const char *name;

  char hex[GIT_MAX_HEXSZ + 1];
  char mode[10];

  /*
   * If this diff_tempfile instance refers to a temporary file,
   * this tempfile object is used to manage its lifetime.
   */
  struct tempfile *tempfile;
} diff_temp[2];

struct emit_callback {
  int color_diff;
  unsigned ws_rule;
  int blank_at_eof_in_preimage;
  int blank_at_eof_in_postimage;
  int lno_in_preimage;
  int lno_in_postimage;
  int last_line_kind;
  const char **label_path;
  struct diff_words_data *diff_words;
  struct diff_options *opt;
  struct strbuf *header;
};

/*
 * State for the line-range callback wrappers that sit between
 * xdi_diff_outf() and fn_out_consume().  xdiff produces a normal,
 * unfiltered diff; the wrappers intercept each hunk header and line,
 * track post-image position, and forward only lines that fall within
 * the requested ranges.  Contiguous in-range lines are collected into
 * range hunks and flushed with a synthetic @@ header so that
 * fn_out_consume() sees well-formed unified-diff fragments.
 *
 * Removal lines ('-') cannot be classified by post-image position, so
 * they are buffered in pending_rm until the next '+' or ' ' line
 * reveals whether they precede an in-range line (flush into range hunk) or
 * an out-of-range line (discard).
 */
struct line_range_callback {
  xdiff_emit_line_fn orig_line_fn;
  void *orig_cb_data;
  const struct range_set *ranges; /* 0-based [start, end) */
  unsigned int cur_range;   /* index into the range_set */

  /* Post/pre-image line counters (1-based, set from hunk headers) */
  long lno_post;
  long lno_pre;

  /*
   * Function name from most recent xdiff hunk header;
   * size matches struct func_line.buf in xdiff/xemit.c.
   */
  char func[80];
  long funclen;

  /* Range hunk being accumulated for the current range */
  struct strbuf rhunk;
  long rhunk_old_begin, rhunk_old_count;
  long rhunk_new_begin, rhunk_new_count;
  int rhunk_active;
  int rhunk_has_changes;    /* any '+' or '-' lines? */

  /* Removal lines not yet known to be in-range */
  struct strbuf pending_rm;
  int pending_rm_count;
  long pending_rm_pre_begin;  /* pre-image line of first pending */

  int ret;      /* latched error from orig_line_fn */
};

static int count_lines(const char *data, int size)
{
  int count, ch, completely_empty = 1, nl_just_seen = 0;
  count = 0;
  while (0 < size--) {
    ch = *data++;
    if (ch == '\n') {
      count++;
      nl_just_seen = 1;
      completely_empty = 0;
    }
    else {
      nl_just_seen = 0;
      completely_empty = 0;
    }
  }
  if (completely_empty)
    return 0;
  if (!nl_just_seen)
    count++; /* no trailing newline */
  return count;
}

static int fill_mmfile(struct repository *r, mmfile_t *mf,
           struct diff_filespec *one)
{
  if (!DIFF_FILE_VALID(one)) {
    mf->ptr = (char *)""; /* does not matter */
    mf->size = 0;
    return 0;
  }
  else if (diff_populate_filespec(r, one, NULL))
    return -1;

  mf->ptr = one->data;
  mf->size = one->size;
  return 0;
}

/* like fill_mmfile, but only for size, so we can avoid retrieving blob */
static unsigned long diff_filespec_size(struct repository *r,
          struct diff_filespec *one)
{
  struct diff_populate_filespec_options dpf_options = {
    .check_size_only = 1,
  };

  if (!DIFF_FILE_VALID(one))
    return 0;
  diff_populate_filespec(r, one, &dpf_options);
  return one->size;
}

static int count_trailing_blank(mmfile_t *mf)
{
  char *ptr = mf->ptr;
  long size = mf->size;
  int cnt = 0;

  if (!size)
    return cnt;
  ptr += size - 1; /* pointing at the very end */
  if (*ptr != '\n')
    ; /* incomplete line */
  else
    ptr--; /* skip the last LF */
  while (mf->ptr < ptr) {
    char *prev_eol;
    for (prev_eol = ptr; mf->ptr <= prev_eol; prev_eol--)
      if (*prev_eol == '\n')
        break;
    if (!ws_blank_line(prev_eol + 1, ptr - prev_eol))
      break;
    cnt++;
    ptr = prev_eol - 1;
  }
  return cnt;
}

static void check_blank_at_eof(mmfile_t *mf1, mmfile_t *mf2,
             struct emit_callback *ecbdata)
{
  int l1, l2, at;
  l1 = count_trailing_blank(mf1);
  l2 = count_trailing_blank(mf2);
  if (l2 <= l1) {
    ecbdata->blank_at_eof_in_preimage = 0;
    ecbdata->blank_at_eof_in_postimage = 0;
    return;
  }
  at = count_lines(mf1->ptr, mf1->size);
  ecbdata->blank_at_eof_in_preimage = (at - l1) + 1;

  at = count_lines(mf2->ptr, mf2->size);
  ecbdata->blank_at_eof_in_postimage = (at - l2) + 1;
}

static void emit_line_0(struct diff_options *o,
      const char *set_sign, const char *set, unsigned reverse, const char *reset,
      int first, const char *line, int len)
{
  int has_trailing_newline, has_trailing_carriage_return;
  int needs_reset = 0; /* at the end of the line */
  FILE *file = o->file;

  fputs(diff_line_prefix(o), file);

  has_trailing_newline = (len > 0 && line[len-1] == '\n');
  if (has_trailing_newline)
    len--;

  has_trailing_carriage_return = (len > 0 && line[len-1] == '\r');
  if (has_trailing_carriage_return)
    len--;

  if (!len && !first)
    goto end_of_line;

  if (reverse && want_color(o->use_color)) {
    fputs(GIT_COLOR_REVERSE, file);
    needs_reset = 1;
  }

  if (set_sign) {
    fputs(set_sign, file);
    needs_reset = 1;
  }

  if (first)
    fputc(first, file);

  if (!len)
    goto end_of_line;

  if (set) {
    if (set_sign && set != set_sign)
      fputs(reset, file);
    fputs(set, file);
    needs_reset = 1;
  }
  fwrite(line, len, 1, file);
  needs_reset = 1; /* 'line' may contain color codes. */

end_of_line:
  if (needs_reset)
    fputs(reset, file);
  if (has_trailing_carriage_return)
    fputc('\r', file);
  if (has_trailing_newline)
    fputc('\n', file);
}

static void emit_line(struct diff_options *o, const char *set, const char *reset,
          const char *line, int len)
{
  emit_line_0(o, set, NULL, 0, reset, 0, line, len);
}

enum diff_symbol {
  DIFF_SYMBOL_BINARY_DIFF_HEADER,
  DIFF_SYMBOL_BINARY_DIFF_HEADER_DELTA,
  DIFF_SYMBOL_BINARY_DIFF_HEADER_LITERAL,
  DIFF_SYMBOL_BINARY_DIFF_BODY,
  DIFF_SYMBOL_BINARY_DIFF_FOOTER,
  DIFF_SYMBOL_STATS_SUMMARY_NO_FILES,
  DIFF_SYMBOL_STATS_SUMMARY_ABBREV,
  DIFF_SYMBOL_STATS_SUMMARY_INSERTS_DELETES,
  DIFF_SYMBOL_STATS_LINE,
  DIFF_SYMBOL_WORD_DIFF,
  DIFF_SYMBOL_STAT_SEP,
  DIFF_SYMBOL_SUMMARY,
  DIFF_SYMBOL_SUBMODULE_ADD,
  DIFF_SYMBOL_SUBMODULE_DEL,
  DIFF_SYMBOL_SUBMODULE_UNTRACKED,
  DIFF_SYMBOL_SUBMODULE_MODIFIED,
  DIFF_SYMBOL_SUBMODULE_HEADER,
  DIFF_SYMBOL_SUBMODULE_ERROR,
  DIFF_SYMBOL_SUBMODULE_PIPETHROUGH,
  DIFF_SYMBOL_REWRITE_DIFF,
  DIFF_SYMBOL_BINARY_FILES,
  DIFF_SYMBOL_HEADER,
  DIFF_SYMBOL_FILEPAIR_PLUS,
  DIFF_SYMBOL_FILEPAIR_MINUS,
  DIFF_SYMBOL_WORDS_PORCELAIN,
  DIFF_SYMBOL_WORDS,
  DIFF_SYMBOL_CONTEXT,
  DIFF_SYMBOL_CONTEXT_INCOMPLETE,
  DIFF_SYMBOL_PLUS,
  DIFF_SYMBOL_MINUS,
  DIFF_SYMBOL_CONTEXT_FRAGINFO,
  DIFF_SYMBOL_CONTEXT_MARKER,
  DIFF_SYMBOL_SEPARATOR
};

/*
 * Flags for content lines:
 * 0..15 are whitespace rules (see ws.h)
 * 16..18 are WSEH_NEW | WSEH_CONTEXT | WSEH_OLD
 * 19 is marking if the line is blank at EOF
 * 20..22 are used for color-moved.
 */
#define DIFF_SYMBOL_CONTENT_BLANK_LINE_EOF  (1<<19)
#define DIFF_SYMBOL_MOVED_LINE      (1<<20)
#define DIFF_SYMBOL_MOVED_LINE_ALT    (1<<21)
#define DIFF_SYMBOL_MOVED_LINE_UNINTERESTING  (1<<22)

#define DIFF_SYMBOL_CONTENT_WS_MASK (WSEH_NEW | WSEH_OLD | WSEH_CONTEXT | WS_RULE_MASK)

/*
 * This struct is used when we need to buffer the output of the diff output.
 *
 * NEEDSWORK: Instead of storing a copy of the line, add an offset pointer
 * into the pre/post image file. This pointer could be a union with the
 * line pointer. By storing an offset into the file instead of the literal line,
 * we can decrease the memory footprint for the buffered output. At first we
 * may want to only have indirection for the content lines, but we could also
 * enhance the state for emitting prefabricated lines, e.g. the similarity
 * score line or hunk/file headers would only need to store a number or path
 * and then the output can be constructed later on depending on state.
 */
struct emitted_diff_symbol {
  const char *line;
  int len;
  int flags;
  int indent_off;   /* Offset to first non-whitespace character */
  int indent_width; /* The visual width of the indentation */
  unsigned id;
  enum diff_symbol s;
};
#define EMITTED_DIFF_SYMBOL_INIT { 0 }

struct emitted_diff_symbols {
  struct emitted_diff_symbol *buf;
  int nr, alloc;
};
#define EMITTED_DIFF_SYMBOLS_INIT { 0 }

static void append_emitted_diff_symbol(struct diff_options *o,
               struct emitted_diff_symbol *e)
{
  struct emitted_diff_symbol *f;

  ALLOC_GROW(o->emitted_symbols->buf,
       o->emitted_symbols->nr + 1,
       o->emitted_symbols->alloc);
  f = &o->emitted_symbols->buf[o->emitted_symbols->nr++];

  memcpy(f, e, sizeof(struct emitted_diff_symbol));
  f->line = e->line ? xmemdupz(e->line, e->len) : NULL;
}

static void free_emitted_diff_symbols(struct emitted_diff_symbols *e)
{
  if (!e)
    return;
  free(e->buf);
  free(e);
}

struct moved_entry {
  const struct emitted_diff_symbol *es;
  struct moved_entry *next_line;
  struct moved_entry *next_match;
};

struct moved_block {
  struct moved_entry *match;
  int wsd; /* The whitespace delta of this block */
};

#define INDENT_BLANKLINE INT_MIN

static void fill_es_indent_data(struct emitted_diff_symbol *es)
{
  unsigned int off = 0, i;
  int width = 0, tab_width = es->flags & WS_TAB_WIDTH_MASK;
  const char *s = es->line;
  const int len = es->len;

  /* skip any \v \f \r at start of indentation */
  while (s[off] == '\f' || s[off] == '\v' ||
         (off < len - 1 && s[off] == '\r'))
    off++;

  /* calculate the visual width of indentation */
  while(1) {
    if (s[off] == ' ') {
      width++;
      off++;
    } else if (s[off] == '\t') {
      width += tab_width - (width % tab_width);
      while (s[++off] == '\t')
        width += tab_width;
    } else {
      break;
    }
  }

  /* check if this line is blank */
  for (i = off; i < len; i++)
    if (!isspace(s[i]))
        break;

  if (i == len) {
    es->indent_width = INDENT_BLANKLINE;
    es->indent_off = len;
  } else {
    es->indent_off = off;
    es->indent_width = width;
  }
}

static int compute_ws_delta(const struct emitted_diff_symbol *a,
          const struct emitted_diff_symbol *b)
{
  int a_width = a->indent_width,
      b_width = b->indent_width;

  if (a_width == INDENT_BLANKLINE && b_width == INDENT_BLANKLINE)
    return INDENT_BLANKLINE;

  return a_width - b_width;
}

static int cmp_in_block_with_wsd(const struct moved_entry *cur,
         const struct emitted_diff_symbol *l,
         struct moved_block *pmb)
{
  int a_width = cur->es->indent_width, b_width = l->indent_width;
  int delta;

  /* The text of each line must match */
  if (cur->es->id != l->id)
    return 1;

  /*
   * If 'l' and 'cur' are both blank then we don't need to check the
   * indent. We only need to check cur as we know the strings match.
   * */
  if (a_width == INDENT_BLANKLINE)
    return 0;

  /*
   * The indent changes of the block are known and stored in pmb->wsd;
   * however we need to check if the indent changes of the current line
   * match those of the current block.
   */
  delta = b_width - a_width;

  /*
   * If the previous lines of this block were all blank then set its
   * whitespace delta.
   */
  if (pmb->wsd == INDENT_BLANKLINE)
    pmb->wsd = delta;

  return delta != pmb->wsd;
}

struct interned_diff_symbol {
  struct hashmap_entry ent;
  struct emitted_diff_symbol *es;
};

static int interned_diff_symbol_cmp(const void *hashmap_cmp_fn_data,
            const struct hashmap_entry *eptr,
            const struct hashmap_entry *entry_or_key,
            const void *keydata UNUSED)
{
  const struct diff_options *diffopt = hashmap_cmp_fn_data;
  const struct emitted_diff_symbol *a, *b;
  unsigned flags = diffopt->color_moved_ws_handling
       & XDF_WHITESPACE_FLAGS;

  a = container_of(eptr, const struct interned_diff_symbol, ent)->es;
  b = container_of(entry_or_key, const struct interned_diff_symbol, ent)->es;

  return !xdiff_compare_lines(a->line + a->indent_off,
            a->len - a->indent_off,
            b->line + b->indent_off,
            b->len - b->indent_off, flags);
}

static void prepare_entry(struct diff_options *o, struct emitted_diff_symbol *l,
        struct interned_diff_symbol *s)
{
  unsigned flags = o->color_moved_ws_handling & XDF_WHITESPACE_FLAGS;
  unsigned int hash = xdiff_hash_string(l->line + l->indent_off,
                l->len - l->indent_off, flags);

  hashmap_entry_init(&s->ent, hash);
  s->es = l;
}

struct moved_entry_list {
  struct moved_entry *add, *del;
};

static struct moved_entry_list *add_lines_to_move_detection(struct diff_options *o,
                  struct mem_pool *entry_mem_pool)
{
  struct moved_entry *prev_line = NULL;
  struct mem_pool interned_pool;
  struct hashmap interned_map;
  struct moved_entry_list *entry_list = NULL;
  size_t entry_list_alloc = 0;
  unsigned id = 0;
  int n;

  hashmap_init(&interned_map, interned_diff_symbol_cmp, o, 8096);
  mem_pool_init(&interned_pool, 1024 * 1024);

  for (n = 0; n < o->emitted_symbols->nr; n++) {
    struct interned_diff_symbol key;
    struct emitted_diff_symbol *l = &o->emitted_symbols->buf[n];
    struct interned_diff_symbol *s;
    struct moved_entry *entry;

    if (l->s != DIFF_SYMBOL_PLUS && l->s != DIFF_SYMBOL_MINUS) {
      prev_line = NULL;
      continue;
    }

    if (o->color_moved_ws_handling &
        COLOR_MOVED_WS_ALLOW_INDENTATION_CHANGE)
      fill_es_indent_data(l);

    prepare_entry(o, l, &key);
    s = hashmap_get_entry(&interned_map, &key, ent, &key.ent);
    if (s) {
      l->id = s->es->id;
    } else {
      l->id = id;
      ALLOC_GROW_BY(entry_list, id, 1, entry_list_alloc);
      hashmap_add(&interned_map,
            memcpy(mem_pool_alloc(&interned_pool,
                sizeof(key)),
             &key, sizeof(key)));
    }
    entry = mem_pool_alloc(entry_mem_pool, sizeof(*entry));
    entry->es = l;
    entry->next_line = NULL;
    if (prev_line && prev_line->es->s == l->s)
      prev_line->next_line = entry;
    prev_line = entry;
    if (l->s == DIFF_SYMBOL_PLUS) {
      entry->next_match = entry_list[l->id].add;
      entry_list[l->id].add = entry;
    } else {
      entry->next_match = entry_list[l->id].del;
      entry_list[l->id].del = entry;
    }
  }

  hashmap_clear(&interned_map);
  mem_pool_discard(&interned_pool, 0);

  return entry_list;
}

static void pmb_advance_or_null(struct diff_options *o,
        struct emitted_diff_symbol *l,
        struct moved_block *pmb,
        int *pmb_nr)
{
  int i, j;

  for (i = 0, j = 0; i < *pmb_nr; i++) {
    int match;
    struct moved_entry *prev = pmb[i].match;
    struct moved_entry *cur = (prev && prev->next_line) ?
        prev->next_line : NULL;

    if (o->color_moved_ws_handling &
        COLOR_MOVED_WS_ALLOW_INDENTATION_CHANGE)
      match = cur &&
        !cmp_in_block_with_wsd(cur, l, &pmb[i]);
    else
      match = cur && cur->es->id == l->id;

    if (match) {
      pmb[j] = pmb[i];
      pmb[j++].match = cur;
    }
  }
  *pmb_nr = j;
}

static void fill_potential_moved_blocks(struct diff_options *o,
          struct moved_entry *match,
          struct emitted_diff_symbol *l,
          struct moved_block **pmb_p,
          int *pmb_alloc_p, int *pmb_nr_p)

{
  struct moved_block *pmb = *pmb_p;
  int pmb_alloc = *pmb_alloc_p, pmb_nr = *pmb_nr_p;

  /*
   * The current line is the start of a new block.
   * Setup the set of potential blocks.
   */
  for (; match; match = match->next_match) {
    ALLOC_GROW(pmb, pmb_nr + 1, pmb_alloc);
    if (o->color_moved_ws_handling &
        COLOR_MOVED_WS_ALLOW_INDENTATION_CHANGE)
      pmb[pmb_nr].wsd = compute_ws_delta(l, match->es);
    else
      pmb[pmb_nr].wsd = 0;
    pmb[pmb_nr++].match = match;
  }

  *pmb_p = pmb;
  *pmb_alloc_p = pmb_alloc;
  *pmb_nr_p = pmb_nr;
}

/*
 * If o->color_moved is COLOR_MOVED_PLAIN, this function does nothing.
 *
 * Otherwise, if the last block has fewer alphanumeric characters than
 * COLOR_MOVED_MIN_ALNUM_COUNT, unset DIFF_SYMBOL_MOVED_LINE on all lines in
 * that block.
 *
 * The last block consists of the (n - block_length)'th line up to but not
 * including the nth line.
 *
 * Returns 0 if the last block is empty or is unset by this function, non zero
 * otherwise.
 *
 * NEEDSWORK: This uses the same heuristic as blame_entry_score() in blame.c.
 * Think of a way to unify them.
 */
#define DIFF_SYMBOL_MOVED_LINE_ZEBRA_MASK \
  (DIFF_SYMBOL_MOVED_LINE | DIFF_SYMBOL_MOVED_LINE_ALT)
static int adjust_last_block(struct diff_options *o, int n, int block_length)
{
  int i, alnum_count = 0;
  if (o->color_moved == COLOR_MOVED_PLAIN)
    return block_length;
  for (i = 1; i < block_length + 1; i++) {
    const char *c = o->emitted_symbols->buf[n - i].line;
    for (; *c; c++) {
      if (!isalnum(*c))
        continue;
      alnum_count++;
      if (alnum_count >= COLOR_MOVED_MIN_ALNUM_COUNT)
        return 1;
    }
  }
  for (i = 1; i < block_length + 1; i++)
    o->emitted_symbols->buf[n - i].flags &= ~DIFF_SYMBOL_MOVED_LINE_ZEBRA_MASK;
  return 0;
}

/* Find blocks of moved code, delegate actual coloring decision to helper */
static void mark_color_as_moved(struct diff_options *o,
        struct moved_entry_list *entry_list)
{
  struct moved_block *pmb = NULL; /* potentially moved blocks */
  int pmb_nr = 0, pmb_alloc = 0;
  int n, flipped_block = 0, block_length = 0;
  enum diff_symbol moved_symbol = DIFF_SYMBOL_BINARY_DIFF_HEADER;


  for (n = 0; n < o->emitted_symbols->nr; n++) {
    struct moved_entry *match = NULL;
    struct emitted_diff_symbol *l = &o->emitted_symbols->buf[n];

    switch (l->s) {
    case DIFF_SYMBOL_PLUS:
      match = entry_list[l->id].del;
      break;
    case DIFF_SYMBOL_MINUS:
      match = entry_list[l->id].add;
      break;
    default:
      flipped_block = 0;
    }

    if (pmb_nr && (!match || l->s != moved_symbol)) {
      if (!adjust_last_block(o, n, block_length) &&
          block_length > 1) {
        /*
         * Rewind in case there is another match
         * starting at the second line of the block
         */
        match = NULL;
        n -= block_length;
      }
      pmb_nr = 0;
      block_length = 0;
      flipped_block = 0;
    }
    if (!match) {
      moved_symbol = DIFF_SYMBOL_BINARY_DIFF_HEADER;
      continue;
    }

    if (o->color_moved == COLOR_MOVED_PLAIN) {
      l->flags |= DIFF_SYMBOL_MOVED_LINE;
      continue;
    }

    pmb_advance_or_null(o, l, pmb, &pmb_nr);

    if (pmb_nr == 0) {
      int contiguous = adjust_last_block(o, n, block_length);

      if (!contiguous && block_length > 1)
        /*
         * Rewind in case there is another match
         * starting at the second line of the block
         */
        n -= block_length;
      else
        fill_potential_moved_blocks(o, match, l,
                  &pmb, &pmb_alloc,
                  &pmb_nr);

      if (contiguous && pmb_nr && moved_symbol == l->s)
        flipped_block = (flipped_block + 1) % 2;
      else
        flipped_block = 0;

      if (pmb_nr)
        moved_symbol = l->s;
      else
        moved_symbol = DIFF_SYMBOL_BINARY_DIFF_HEADER;

      block_length = 0;
    }

    if (pmb_nr) {
      block_length++;
      l->flags |= DIFF_SYMBOL_MOVED_LINE;
      if (flipped_block && o->color_moved != COLOR_MOVED_BLOCKS)
        l->flags |= DIFF_SYMBOL_MOVED_LINE_ALT;
    }
  }
  adjust_last_block(o, n, block_length);

  free(pmb);
}

static void dim_moved_lines(struct diff_options *o)
{
  int n;
  for (n = 0; n < o->emitted_symbols->nr; n++) {
    struct emitted_diff_symbol *prev = (n != 0) ?
        &o->emitted_symbols->buf[n - 1] : NULL;
    struct emitted_diff_symbol *l = &o->emitted_symbols->buf[n];
    struct emitted_diff_symbol *next =
        (n < o->emitted_symbols->nr - 1) ?
        &o->emitted_symbols->buf[n + 1] : NULL;

    /* Not a plus or minus line? */
    if (l->s != DIFF_SYMBOL_PLUS && l->s != DIFF_SYMBOL_MINUS)
      continue;

    /* Not a moved line? */
    if (!(l->flags & DIFF_SYMBOL_MOVED_LINE))
      continue;

    /*
     * If prev or next are not a plus or minus line,
     * pretend they don't exist
     */
    if (prev && prev->s != DIFF_SYMBOL_PLUS &&
          prev->s != DIFF_SYMBOL_MINUS)
      prev = NULL;
    if (next && next->s != DIFF_SYMBOL_PLUS &&
          next->s != DIFF_SYMBOL_MINUS)
      next = NULL;

    /* Inside a block? */
    if ((prev &&
        (prev->flags & DIFF_SYMBOL_MOVED_LINE_ZEBRA_MASK) ==
        (l->flags & DIFF_SYMBOL_MOVED_LINE_ZEBRA_MASK)) &&
        (next &&
        (next->flags & DIFF_SYMBOL_MOVED_LINE_ZEBRA_MASK) ==
        (l->flags & DIFF_SYMBOL_MOVED_LINE_ZEBRA_MASK))) {
      l->flags |= DIFF_SYMBOL_MOVED_LINE_UNINTERESTING;
      continue;
    }

    /* Check if we are at an interesting bound: */
    if (prev && (prev->flags & DIFF_SYMBOL_MOVED_LINE) &&
        (prev->flags & DIFF_SYMBOL_MOVED_LINE_ALT) !=
           (l->flags & DIFF_SYMBOL_MOVED_LINE_ALT))
      continue;
    if (next && (next->flags & DIFF_SYMBOL_MOVED_LINE) &&
        (next->flags & DIFF_SYMBOL_MOVED_LINE_ALT) !=
           (l->flags & DIFF_SYMBOL_MOVED_LINE_ALT))
      continue;

    /*
     * The boundary to prev and next are not interesting,
     * so this line is not interesting as a whole
     */
    l->flags |= DIFF_SYMBOL_MOVED_LINE_UNINTERESTING;
  }
}

static void emit_line_ws_markup(struct diff_options *o,
        const char *set_sign, const char *set,
        const char *reset,
        int sign_index, const char *line, int len,
        unsigned ws_rule, int blank_at_eof)
{
  const char *ws = NULL;
  int sign = o->output_indicators[sign_index];

  if (diff_suppress_blank_empty &&
      sign_index == OUTPUT_INDICATOR_CONTEXT &&
      len == 1 && line[0] == '\n')
    sign = 0;

  if (o->ws_error_highlight & ws_rule) {
    ws = diff_get_color_opt(o, DIFF_WHITESPACE);
    if (!*ws)
      ws = NULL;
  }

  if (!ws && !set_sign) {
    emit_line_0(o, set, NULL, 0, reset, sign, line, len);
  } else if (!ws) {
    emit_line_0(o, set_sign, set, !!set_sign, reset, sign, line, len);
  } else if (blank_at_eof) {
    /* Blank line at EOF - paint '+' as well */
    emit_line_0(o, ws, NULL, 0, reset, sign, line, len);
  } else {
    /* Emit just the prefix, then the rest. */
    emit_line_0(o, set_sign ? set_sign : set, NULL, !!set_sign, reset,
          sign, "", 0);
    ws_check_emit(line, len, ws_rule,
            o->file, set, reset, ws);
  }
}

static void emit_diff_symbol_from_struct(struct diff_options *o,
           struct emitted_diff_symbol *eds)
{
  const char *context, *reset, *set, *set_sign, *meta, *fraginfo;

  enum diff_symbol s = eds->s;
  const char *line = eds->line;
  int len = eds->len;
  unsigned flags = eds->flags;

  if (!o->file)
    return;

  switch (s) {
  case DIFF_SYMBOL_SUBMODULE_HEADER:
  case DIFF_SYMBOL_SUBMODULE_ERROR:
  case DIFF_SYMBOL_SUBMODULE_PIPETHROUGH:
  case DIFF_SYMBOL_STATS_SUMMARY_INSERTS_DELETES:
  case DIFF_SYMBOL_SUMMARY:
  case DIFF_SYMBOL_STATS_LINE:
  case DIFF_SYMBOL_BINARY_DIFF_BODY:
  case DIFF_SYMBOL_CONTEXT_FRAGINFO:
    emit_line(o, "", "", line, len);
    break;
  case DIFF_SYMBOL_CONTEXT_INCOMPLETE:
    if ((flags & WS_INCOMPLETE_LINE) &&
        (flags & o->ws_error_highlight))
      set = diff_get_color_opt(o, DIFF_WHITESPACE);
    else
      set = diff_get_color_opt(o, DIFF_CONTEXT);
    reset = diff_get_color_opt(o, DIFF_RESET);
    emit_line(o, set, reset, line, len);
    break;
  case DIFF_SYMBOL_CONTEXT_MARKER:
    context = diff_get_color_opt(o, DIFF_CONTEXT);
    reset = diff_get_color_opt(o, DIFF_RESET);
    emit_line(o, context, reset, line, len);
    break;
  case DIFF_SYMBOL_SEPARATOR:
    fprintf(o->file, "%s%c",
      diff_line_prefix(o),
      o->line_termination);
    break;
  case DIFF_SYMBOL_CONTEXT:
    set = diff_get_color_opt(o, DIFF_CONTEXT);
    reset = diff_get_color_opt(o, DIFF_RESET);
    set_sign = NULL;
    if (o->flags.dual_color_diffed_diffs) {
      char c = !len ? 0 : line[0];

      if (c == '+')
        set = diff_get_color_opt(o, DIFF_FILE_NEW);
      else if (c == '@')
        set = diff_get_color_opt(o, DIFF_FRAGINFO);
      else if (c == '-')
        set = diff_get_color_opt(o, DIFF_FILE_OLD);
    }
    emit_line_ws_markup(o, set_sign, set, reset,
            OUTPUT_INDICATOR_CONTEXT, line, len,
            flags & (DIFF_SYMBOL_CONTENT_WS_MASK), 0);
    break;
  case DIFF_SYMBOL_PLUS:
    switch (flags & (DIFF_SYMBOL_MOVED_LINE |
         DIFF_SYMBOL_MOVED_LINE_ALT |
         DIFF_SYMBOL_MOVED_LINE_UNINTERESTING)) {
    case DIFF_SYMBOL_MOVED_LINE |
         DIFF_SYMBOL_MOVED_LINE_ALT |
         DIFF_SYMBOL_MOVED_LINE_UNINTERESTING:
      set = diff_get_color_opt(o, DIFF_FILE_NEW_MOVED_ALT_DIM);
      break;
    case DIFF_SYMBOL_MOVED_LINE |
         DIFF_SYMBOL_MOVED_LINE_ALT:
      set = diff_get_color_opt(o, DIFF_FILE_NEW_MOVED_ALT);
      break;
    case DIFF_SYMBOL_MOVED_LINE |
         DIFF_SYMBOL_MOVED_LINE_UNINTERESTING:
      set = diff_get_color_opt(o, DIFF_FILE_NEW_MOVED_DIM);
      break;
    case DIFF_SYMBOL_MOVED_LINE:
      set = diff_get_color_opt(o, DIFF_FILE_NEW_MOVED);
      break;
    default:
      set = diff_get_color_opt(o, DIFF_FILE_NEW);
    }
    reset = diff_get_color_opt(o, DIFF_RESET);
    if (!o->flags.dual_color_diffed_diffs)
      set_sign = NULL;
    else {
      char c = !len ? 0 : line[0];

      set_sign = set;
      if (c == '-')
        set = diff_get_color_opt(o, DIFF_FILE_OLD_BOLD);
      else if (c == '@')
        set = diff_get_color_opt(o, DIFF_FRAGINFO);
      else if (c == '+')
        set = diff_get_color_opt(o, DIFF_FILE_NEW_BOLD);
      else
        set = diff_get_color_opt(o, DIFF_CONTEXT_BOLD);
      flags &= ~DIFF_SYMBOL_CONTENT_WS_MASK;
    }
    emit_line_ws_markup(o, set_sign, set, reset,
            OUTPUT_INDICATOR_NEW, line, len,
            flags & DIFF_SYMBOL_CONTENT_WS_MASK,
            flags & DIFF_SYMBOL_CONTENT_BLANK_LINE_EOF);
    break;
  case DIFF_SYMBOL_MINUS:
    switch (flags & (DIFF_SYMBOL_MOVED_LINE |
         DIFF_SYMBOL_MOVED_LINE_ALT |
         DIFF_SYMBOL_MOVED_LINE_UNINTERESTING)) {
    case DIFF_SYMBOL_MOVED_LINE |
         DIFF_SYMBOL_MOVED_LINE_ALT |
         DIFF_SYMBOL_MOVED_LINE_UNINTERESTING:
      set = diff_get_color_opt(o, DIFF_FILE_OLD_MOVED_ALT_DIM);
      break;
    case DIFF_SYMBOL_MOVED_LINE |
         DIFF_SYMBOL_MOVED_LINE_ALT:
      set = diff_get_color_opt(o, DIFF_FILE_OLD_MOVED_ALT);
      break;
    case DIFF_SYMBOL_MOVED_LINE |
         DIFF_SYMBOL_MOVED_LINE_UNINTERESTING:
      set = diff_get_color_opt(o, DIFF_FILE_OLD_MOVED_DIM);
      break;
    case DIFF_SYMBOL_MOVED_LINE:
      set = diff_get_color_opt(o, DIFF_FILE_OLD_MOVED);
      break;
    default:
      set = diff_get_color_opt(o, DIFF_FILE_OLD);
    }
    reset = diff_get_color_opt(o, DIFF_RESET);
    if (!o->flags.dual_color_diffed_diffs)
      set_sign = NULL;
    else {
      char c = !len ? 0 : line[0];

      set_sign = set;
      if (c == '+')
        set = diff_get_color_opt(o, DIFF_FILE_NEW_DIM);
      else if (c == '@')
        set = diff_get_color_opt(o, DIFF_FRAGINFO);
      else if (c == '-')
        set = diff_get_color_opt(o, DIFF_FILE_OLD_DIM);
      else
        set = diff_get_color_opt(o, DIFF_CONTEXT_DIM);
    }
    emit_line_ws_markup(o, set_sign, set, reset,
            OUTPUT_INDICATOR_OLD, line, len,
            flags & DIFF_SYMBOL_CONTENT_WS_MASK, 0);
    break;
  case DIFF_SYMBOL_WORDS_PORCELAIN:
    context = diff_get_color_opt(o, DIFF_CONTEXT);
    reset = diff_get_color_opt(o, DIFF_RESET);
    emit_line(o, context, reset, line, len);
    fputs("~\n", o->file);
    break;
  case DIFF_SYMBOL_WORDS:
    context = diff_get_color_opt(o, DIFF_CONTEXT);
    reset = diff_get_color_opt(o, DIFF_RESET);

    /* Skip the prefix character */
    line++; len--;
    emit_line(o, context, reset, line, len);
    break;
  case DIFF_SYMBOL_FILEPAIR_PLUS:
    meta = diff_get_color_opt(o, DIFF_METAINFO);
    reset = diff_get_color_opt(o, DIFF_RESET);
    fprintf(o->file, "%s%s+++ %s%s%s\n", diff_line_prefix(o), meta,
      line, reset,
      strchr(line, ' ') ? "\t" : "");
    break;
  case DIFF_SYMBOL_FILEPAIR_MINUS:
    meta = diff_get_color_opt(o, DIFF_METAINFO);
    reset = diff_get_color_opt(o, DIFF_RESET);
    fprintf(o->file, "%s%s--- %s%s%s\n", diff_line_prefix(o), meta,
      line, reset,
      strchr(line, ' ') ? "\t" : "");
    break;
  case DIFF_SYMBOL_BINARY_FILES:
  case DIFF_SYMBOL_HEADER:
    fprintf(o->file, "%s", line);
    break;
  case DIFF_SYMBOL_BINARY_DIFF_HEADER:
    fprintf(o->file, "%sGIT binary patch\n", diff_line_prefix(o));
    break;
  case DIFF_SYMBOL_BINARY_DIFF_HEADER_DELTA:
    fprintf(o->file, "%sdelta %s\n", diff_line_prefix(o), line);
    break;
  case DIFF_SYMBOL_BINARY_DIFF_HEADER_LITERAL:
    fprintf(o->file, "%sliteral %s\n", diff_line_prefix(o), line);
    break;
  case DIFF_SYMBOL_BINARY_DIFF_FOOTER:
    fputs(diff_line_prefix(o), o->file);
    fputc('\n', o->file);
    break;
  case DIFF_SYMBOL_REWRITE_DIFF:
    fraginfo = diff_get_color(o->use_color, DIFF_FRAGINFO);
    reset = diff_get_color_opt(o, DIFF_RESET);
    emit_line(o, fraginfo, reset, line, len);
    break;
  case DIFF_SYMBOL_SUBMODULE_ADD:
    set = diff_get_color_opt(o, DIFF_FILE_NEW);
    reset = diff_get_color_opt(o, DIFF_RESET);
    emit_line(o, set, reset, line, len);
    break;
  case DIFF_SYMBOL_SUBMODULE_DEL:
    set = diff_get_color_opt(o, DIFF_FILE_OLD);
    reset = diff_get_color_opt(o, DIFF_RESET);
    emit_line(o, set, reset, line, len);
    break;
  case DIFF_SYMBOL_SUBMODULE_UNTRACKED:
    fprintf(o->file, "%sSubmodule %s contains untracked content\n",
      diff_line_prefix(o), line);
    break;
  case DIFF_SYMBOL_SUBMODULE_MODIFIED:
    fprintf(o->file, "%sSubmodule %s contains modified content\n",
      diff_line_prefix(o), line);
    break;
  case DIFF_SYMBOL_STATS_SUMMARY_NO_FILES:
    emit_line(o, "", "", " 0 files changed\n",
        strlen(" 0 files changed\n"));
    break;
  case DIFF_SYMBOL_STATS_SUMMARY_ABBREV:
    emit_line(o, "", "", " ...\n", strlen(" ...\n"));
    break;
  case DIFF_SYMBOL_WORD_DIFF:
    fprintf(o->file, "%.*s", len, line);
    break;
  case DIFF_SYMBOL_STAT_SEP:
    fputs(o->stat_sep, o->file);
    break;
  default:
    BUG("unknown diff symbol");
  }
}

static void emit_diff_symbol(struct diff_options *o, enum diff_symbol s,
           const char *line, int len, unsigned flags)
{
  struct emitted_diff_symbol e = {
    .line = line, .len = len, .flags = flags, .s = s
  };

  if (o->emitted_symbols)
    append_emitted_diff_symbol(o, &e);
  else
    emit_diff_symbol_from_struct(o, &e);
}

void diff_emit_submodule_del(struct diff_options *o, const char *line)
{
  emit_diff_symbol(o, DIFF_SYMBOL_SUBMODULE_DEL, line, strlen(line), 0);
}

void diff_emit_submodule_add(struct diff_options *o, const char *line)
{
  emit_diff_symbol(o, DIFF_SYMBOL_SUBMODULE_ADD, line, strlen(line), 0);
}

void diff_emit_submodule_untracked(struct diff_options *o, const char *path)
{
  emit_diff_symbol(o, DIFF_SYMBOL_SUBMODULE_UNTRACKED,
       path, strlen(path), 0);
}

void diff_emit_submodule_modified(struct diff_options *o, const char *path)
{
  emit_diff_symbol(o, DIFF_SYMBOL_SUBMODULE_MODIFIED,
       path, strlen(path), 0);
}

void diff_emit_submodule_header(struct diff_options *o, const char *header)
{
  emit_diff_symbol(o, DIFF_SYMBOL_SUBMODULE_HEADER,
       header, strlen(header), 0);
}

void diff_emit_submodule_error(struct diff_options *o, const char *err)
{
  emit_diff_symbol(o, DIFF_SYMBOL_SUBMODULE_ERROR, err, strlen(err), 0);
}

void diff_emit_submodule_pipethrough(struct diff_options *o,
             const char *line, int len)
{
  emit_diff_symbol(o, DIFF_SYMBOL_SUBMODULE_PIPETHROUGH, line, len, 0);
}

static int new_blank_line_at_eof(struct emit_callback *ecbdata, const char *line, int len)
{
  if (!((ecbdata->ws_rule & WS_BLANK_AT_EOF) &&
        ecbdata->blank_at_eof_in_preimage &&
        ecbdata->blank_at_eof_in_postimage &&
        ecbdata->blank_at_eof_in_preimage <= ecbdata->lno_in_preimage &&
        ecbdata->blank_at_eof_in_postimage <= ecbdata->lno_in_postimage))
    return 0;
  return ws_blank_line(line, len);
}

static void emit_add_line(struct emit_callback *ecbdata,
        const char *line, int len)
{
  unsigned flags = WSEH_NEW | ecbdata->ws_rule;
  if (new_blank_line_at_eof(ecbdata, line, len))
    flags |= DIFF_SYMBOL_CONTENT_BLANK_LINE_EOF;

  emit_diff_symbol(ecbdata->opt, DIFF_SYMBOL_PLUS, line, len, flags);
}

static void emit_del_line(struct emit_callback *ecbdata,
        const char *line, int len)
{
  unsigned flags = WSEH_OLD | ecbdata->ws_rule;
  emit_diff_symbol(ecbdata->opt, DIFF_SYMBOL_MINUS, line, len, flags);
}

static void emit_context_line(struct emit_callback *ecbdata,
            const char *line, int len)
{
  unsigned flags = WSEH_CONTEXT | ecbdata->ws_rule;
  emit_diff_symbol(ecbdata->opt, DIFF_SYMBOL_CONTEXT, line, len, flags);
}

static void emit_incomplete_line_marker(struct emit_callback *ecbdata,
          const char *line, int len)
{
  int last_line_kind = ecbdata->last_line_kind;
  unsigned flags = (last_line_kind == '+'
        ? WSEH_NEW
        : last_line_kind == '-'
        ? WSEH_OLD
        : WSEH_CONTEXT) | ecbdata->ws_rule;
  emit_diff_symbol(ecbdata->opt, DIFF_SYMBOL_CONTEXT_INCOMPLETE,
       line, len, flags);
}

static void emit_hunk_header(struct emit_callback *ecbdata,
           const char *line, int len)
{
  const char *context = diff_get_color(ecbdata->color_diff, DIFF_CONTEXT);
  const char *frag = diff_get_color(ecbdata->color_diff, DIFF_FRAGINFO);
  const char *func = diff_get_color(ecbdata->color_diff, DIFF_FUNCINFO);
  const char *reset = diff_get_color(ecbdata->color_diff, DIFF_RESET);
  const char *reverse = want_color(ecbdata->color_diff) ? GIT_COLOR_REVERSE : "";
  static const char atat[2] = { '@', '@' };
  const char *cp, *ep;
  struct strbuf msgbuf = STRBUF_INIT;
  int org_len = len;
  int i = 1;

  /*
   * As a hunk header must begin with "@@ -<old>, +<new> @@",
   * it always is at least 10 bytes long.
   */
  if (len < 10 ||
      memcmp(line, atat, 2) ||
      !(ep = memmem(line + 2, len - 2, atat, 2))) {
    emit_diff_symbol(ecbdata->opt,
         DIFF_SYMBOL_CONTEXT_MARKER, line, len, 0);
    return;
  }
  ep += 2; /* skip over @@ */

  /* The hunk header in fraginfo color */
  if (ecbdata->opt->flags.dual_color_diffed_diffs)
    strbuf_addstr(&msgbuf, reverse);
  strbuf_addstr(&msgbuf, frag);
  if (ecbdata->opt->flags.suppress_hunk_header_line_count)
    strbuf_add(&msgbuf, atat, sizeof(atat));
  else
    strbuf_add(&msgbuf, line, ep - line);
  strbuf_addstr(&msgbuf, reset);

  /*
   * trailing "\r\n"
   */
  for ( ; i < 3; i++)
    if (line[len - i] == '\r' || line[len - i] == '\n')
      len--;

  /* blank before the func header */
  for (cp = ep; ep - line < len; ep++)
    if (*ep != ' ' && *ep != '\t')
      break;
  if (ep != cp) {
    strbuf_addstr(&msgbuf, context);
    strbuf_add(&msgbuf, cp, ep - cp);
    strbuf_addstr(&msgbuf, reset);
  }

  if (ep < line + len) {
    strbuf_addstr(&msgbuf, func);
    strbuf_add(&msgbuf, ep, line + len - ep);
    strbuf_addstr(&msgbuf, reset);
  }

  strbuf_add(&msgbuf, line + len, org_len - len);
  strbuf_complete_line(&msgbuf);
  emit_diff_symbol(ecbdata->opt,
       DIFF_SYMBOL_CONTEXT_FRAGINFO, msgbuf.buf, msgbuf.len, 0);
  strbuf_release(&msgbuf);
}

static struct diff_tempfile *claim_diff_tempfile(void)
{
  int i;
  for (i = 0; i < ARRAY_SIZE(diff_temp); i++)
    if (!diff_temp[i].name)
      return diff_temp + i;
  BUG("diff is failing to clean up its tempfiles");
}

static void remove_tempfile(void)
{
  int i;
  for (i = 0; i < ARRAY_SIZE(diff_temp); i++) {
    if (is_tempfile_active(diff_temp[i].tempfile))
      delete_tempfile(&diff_temp[i].tempfile);
    diff_temp[i].name = NULL;
  }
}

static void add_line_count(struct strbuf *out, int count)
{
  switch (count) {
  case 0:
    strbuf_addstr(out, "0,0");
    break;
  case 1:
    strbuf_addstr(out, "1");
    break;
  default:
    strbuf_addf(out, "1,%d", count);
    break;
  }
}

static void emit_rewrite_lines(struct emit_callback *ecbdata,
             int prefix, const char *data, int size)
{
  const char *endp = NULL;

  while (0 < size) {
    int len, plen;
    char *pdata = NULL;

    endp = memchr(data, '\n', size);

    if (endp) {
      len = endp - data + 1;
      plen = len;
    } else {
      len = size;
      plen = len + 1;
      pdata = xmalloc(plen + 2);
      memcpy(pdata, data, len);
      pdata[len] = '\n';
      pdata[len + 1] = '\0';
    }
    if (prefix != '+') {
      ecbdata->lno_in_preimage++;
      emit_del_line(ecbdata, pdata ? pdata : data, plen);
    } else {
      ecbdata->lno_in_postimage++;
      emit_add_line(ecbdata, pdata ? pdata : data, plen);
    }
    free(pdata);
    size -= len;
    data += len;
  }
  if (!endp) {
    static const char nneof[] = "\\ No newline at end of file\n";
    ecbdata->last_line_kind = prefix;
    emit_incomplete_line_marker(ecbdata, nneof, sizeof(nneof) - 1);
  }
}

static void emit_rewrite_diff(const char *name_a,
            const char *name_b,
            struct diff_filespec *one,
            struct diff_filespec *two,
            struct userdiff_driver *textconv_one,
            struct userdiff_driver *textconv_two,
            struct diff_options *o)
{
  int lc_a, lc_b;
  static struct strbuf a_name = STRBUF_INIT, b_name = STRBUF_INIT;
  const char *a_prefix, *b_prefix;
  char *data_one, *data_two;
  size_t size_one, size_two;
  unsigned ws_rule;
  struct emit_callback ecbdata;
  struct strbuf out = STRBUF_INIT;

  if (diff_mnemonic_prefix && o->flags.reverse_diff) {
    a_prefix = o->b_prefix;
    b_prefix = o->a_prefix;
  } else {
    a_prefix = o->a_prefix;
    b_prefix = o->b_prefix;
  }

  name_a += (*name_a == '/');
  name_b += (*name_b == '/');

  strbuf_reset(&a_name);
  strbuf_reset(&b_name);
  quote_two_c_style(&a_name, a_prefix, name_a, 0);
  quote_two_c_style(&b_name, b_prefix, name_b, 0);

  size_one = fill_textconv(o->repo, textconv_one, one, &data_one);
  size_two = fill_textconv(o->repo, textconv_two, two, &data_two);

  ws_rule = whitespace_rule(o->repo->index, name_b);

  /* symlink being an incomplete line is not a news */
  if (DIFF_FILE_VALID(two) && S_ISLNK(two->mode))
    ws_rule &= ~WS_INCOMPLETE_LINE;

  memset(&ecbdata, 0, sizeof(ecbdata));
  ecbdata.color_diff = o->use_color;
  ecbdata.ws_rule = ws_rule;
  ecbdata.opt = o;
  if (ecbdata.ws_rule & WS_BLANK_AT_EOF) {
    mmfile_t mf1, mf2;
    mf1.ptr = (char *)data_one;
    mf2.ptr = (char *)data_two;
    mf1.size = size_one;
    mf2.size = size_two;
    check_blank_at_eof(&mf1, &mf2, &ecbdata);
  }
  ecbdata.lno_in_preimage = 1;
  ecbdata.lno_in_postimage = 1;

  lc_a = count_lines(data_one, size_one);
  lc_b = count_lines(data_two, size_two);

  emit_diff_symbol(o, DIFF_SYMBOL_FILEPAIR_MINUS,
       a_name.buf, a_name.len, 0);
  emit_diff_symbol(o, DIFF_SYMBOL_FILEPAIR_PLUS,
       b_name.buf, b_name.len, 0);

  strbuf_addstr(&out, "@@ -");
  if (!o->irreversible_delete)
    add_line_count(&out, lc_a);
  else
    strbuf_addstr(&out, "?,?");
  strbuf_addstr(&out, " +");
  add_line_count(&out, lc_b);
  strbuf_addstr(&out, " @@\n");
  emit_diff_symbol(o, DIFF_SYMBOL_REWRITE_DIFF, out.buf, out.len, 0);
  strbuf_release(&out);

  if (lc_a && !o->irreversible_delete)
    emit_rewrite_lines(&ecbdata, '-', data_one, size_one);
  if (lc_b)
    emit_rewrite_lines(&ecbdata, '+', data_two, size_two);
  if (textconv_one)
    free((char *)data_one);
  if (textconv_two)
    free((char *)data_two);
}

struct diff_words_buffer {
  mmfile_t text;
  unsigned long alloc;
  struct diff_words_orig {
    const char *begin, *end;
  } *orig;
  int orig_nr, orig_alloc;
};

static void diff_words_append(char *line, unsigned long len,
    struct diff_words_buffer *buffer)
{
  ALLOC_GROW(buffer->text.ptr, buffer->text.size + len, buffer->alloc);
  line++;
  len--;
  memcpy(buffer->text.ptr + buffer->text.size, line, len);
  buffer->text.size += len;
  buffer->text.ptr[buffer->text.size] = '\0';
}

struct diff_words_style_elem {
  const char *prefix;
  const char *suffix;
  const char *color; /* NULL; filled in by the setup code if
          * color is enabled */
};

struct diff_words_style {
  enum diff_words_type type;
  struct diff_words_style_elem new_word, old_word, ctx;
  const char *newline;
};

static struct diff_words_style diff_words_styles[] = {
  { DIFF_WORDS_PORCELAIN, {"+", "\n"}, {"-", "\n"}, {" ", "\n"}, "~\n" },
  { DIFF_WORDS_PLAIN, {"{+", "+}"}, {"[-", "-]"}, {"", ""}, "\n" },
  { DIFF_WORDS_COLOR, {"", ""}, {"", ""}, {"", ""}, "\n" }
};

struct diff_words_data {
  struct diff_words_buffer minus, plus;
  const char *current_plus;
  int last_minus;
  struct diff_options *opt;
  regex_t *word_regex;
  enum diff_words_type type;
  struct diff_words_style *style;
};

static int fn_out_diff_words_write_helper(struct diff_options *o,
            struct diff_words_style_elem *st_el,
            const char *newline,
            size_t count, const char *buf)
{
  int print = 0;
  struct strbuf sb = STRBUF_INIT;

  while (count) {
    const char *p = memchr(buf, '\n', count);
    if (print)
      strbuf_addstr(&sb, diff_line_prefix(o));

    if (p != buf) {
      const char *reset = st_el->color && *st_el->color ?
              GIT_COLOR_RESET : NULL;
      if (st_el->color && *st_el->color)
        strbuf_addstr(&sb, st_el->color);
      strbuf_addstr(&sb, st_el->prefix);
      strbuf_add(&sb, buf, p ? p - buf : count);
      strbuf_addstr(&sb, st_el->suffix);
      if (reset)
        strbuf_addstr(&sb, reset);
    }
    if (!p)
      goto out;

    strbuf_addstr(&sb, newline);
    count -= p + 1 - buf;
    buf = p + 1;
    print = 1;
    if (count) {
      emit_diff_symbol(o, DIFF_SYMBOL_WORD_DIFF,
           sb.buf, sb.len, 0);
      strbuf_reset(&sb);
    }
  }

out:
  if (sb.len)
    emit_diff_symbol(o, DIFF_SYMBOL_WORD_DIFF,
         sb.buf, sb.len, 0);
  strbuf_release(&sb);
  return 0;
}

/*
 * '--color-words' algorithm can be described as:
 *
 *   1. collect the minus/plus lines of a diff hunk, divided into
 *      minus-lines and plus-lines;
 *
 *   2. break both minus-lines and plus-lines into words and
 *      place them into two mmfile_t with one word for each line;
 *
 *   3. use xdiff to run diff on the two mmfile_t to get the words level diff;
 *
 * And for the common parts of the both file, we output the plus side text.
 * diff_words->current_plus is used to trace the current position of the plus file
 * which printed. diff_words->last_minus is used to trace the last minus word
 * printed.
 *
 * For '--graph' to work with '--color-words', we need to output the graph prefix
 * on each line of color words output. Generally, there are two conditions on
 * which we should output the prefix.
 *
 *   1. diff_words->last_minus == 0 &&
 *      diff_words->current_plus == diff_words->plus.text.ptr
 *
 *      that is: the plus text must start as a new line, and if there is no minus
 *      word printed, a graph prefix must be printed.
 *
 *   2. diff_words->current_plus > diff_words->plus.text.ptr &&
 *      *(diff_words->current_plus - 1) == '\n'
 *
 *      that is: a graph prefix must be printed following a '\n'
 */
static int color_words_output_graph_prefix(struct diff_words_data *diff_words)
{
  if ((diff_words->last_minus == 0 &&
    diff_words->current_plus == diff_words->plus.text.ptr) ||
    (diff_words->current_plus > diff_words->plus.text.ptr &&
    *(diff_words->current_plus - 1) == '\n')) {
    return 1;
  } else {
    return 0;
  }
}

static void fn_out_diff_words_aux(void *priv,
          long minus_first, long minus_len,
          long plus_first, long plus_len,
          const char *func UNUSED, long funclen UNUSED)
{
  struct diff_words_data *diff_words = priv;
  struct diff_words_style *style = diff_words->style;
  const char *minus_begin, *minus_end, *plus_begin, *plus_end;
  struct diff_options *opt = diff_words->opt;
  const char *line_prefix;

  assert(opt);
  line_prefix = diff_line_prefix(opt);

  /* POSIX requires that first be decremented by one if len == 0... */
  if (minus_len) {
    minus_begin = diff_words->minus.orig[minus_first].begin;
    minus_end =
      diff_words->minus.orig[minus_first + minus_len - 1].end;
  } else
    minus_begin = minus_end =
      diff_words->minus.orig[minus_first].end;

  if (plus_len) {
    plus_begin = diff_words->plus.orig[plus_first].begin;
    plus_end = diff_words->plus.orig[plus_first + plus_len - 1].end;
  } else
    plus_begin = plus_end = diff_words->plus.orig[plus_first].end;

  if (color_words_output_graph_prefix(diff_words)) {
    fputs(line_prefix, diff_words->opt->file);
  }
  if (diff_words->current_plus != plus_begin) {
    fn_out_diff_words_write_helper(diff_words->opt,
        &style->ctx, style->newline,
        plus_begin - diff_words->current_plus,
        diff_words->current_plus);
  }
  if (minus_begin != minus_end) {
    fn_out_diff_words_write_helper(diff_words->opt,
        &style->old_word, style->newline,
        minus_end - minus_begin, minus_begin);
  }
  if (plus_begin != plus_end) {
    fn_out_diff_words_write_helper(diff_words->opt,
        &style->new_word, style->newline,
        plus_end - plus_begin, plus_begin);
  }

  diff_words->current_plus = plus_end;
  diff_words->last_minus = minus_first;
}

/* This function starts looking at *begin, and returns 0 iff a word was found. */
static int find_word_boundaries(mmfile_t *buffer, regex_t *word_regex,
    int *begin, int *end)
{
  while (word_regex && *begin < buffer->size) {
    regmatch_t match[1];
    if (!regexec_buf(word_regex, buffer->ptr + *begin,
         buffer->size - *begin, 1, match, 0)) {
      char *p = memchr(buffer->ptr + *begin + match[0].rm_so,
          '\n', match[0].rm_eo - match[0].rm_so);
      *end = p ? p - buffer->ptr : match[0].rm_eo + *begin;
      *begin += match[0].rm_so;
      if (*begin == *end)
        (*begin)++;
      else
        return *begin > *end;
    } else {
      return -1;
    }
  }

  /* find the next word */
  while (*begin < buffer->size && isspace(buffer->ptr[*begin]))
    (*begin)++;
  if (*begin >= buffer->size)
    return -1;

  /* find the end of the word */
  *end = *begin + 1;
  while (*end < buffer->size && !isspace(buffer->ptr[*end]))
    (*end)++;

  return 0;
}

/*
 * This function splits the words in buffer->text, stores the list with
 * newline separator into out, and saves the offsets of the original words
 * in buffer->orig.
 */
static void diff_words_fill(struct diff_words_buffer *buffer, mmfile_t *out,
    regex_t *word_regex)
{
  int i, j;
  long alloc = 0;

  out->size = 0;
  out->ptr = NULL;

  /* fake an empty "0th" word */
  ALLOC_GROW(buffer->orig, 1, buffer->orig_alloc);
  buffer->orig[0].begin = buffer->orig[0].end = buffer->text.ptr;
  buffer->orig_nr = 1;

  for (i = 0; i < buffer->text.size; i++) {
    if (find_word_boundaries(&buffer->text, word_regex, &i, &j))
      return;

    /* store original boundaries */
    ALLOC_GROW(buffer->orig, buffer->orig_nr + 1,
        buffer->orig_alloc);
    buffer->orig[buffer->orig_nr].begin = buffer->text.ptr + i;
    buffer->orig[buffer->orig_nr].end = buffer->text.ptr + j;
    buffer->orig_nr++;

    /* store one word */
    ALLOC_GROW(out->ptr, out->size + j - i + 1, alloc);
    memcpy(out->ptr + out->size, buffer->text.ptr + i, j - i);
    out->ptr[out->size + j - i] = '\n';
    out->size += j - i + 1;

    i = j - 1;
  }
}

/* this executes the word diff on the accumulated buffers */
static void diff_words_show(struct diff_words_data *diff_words)
{
  xpparam_t xpp;
  xdemitconf_t xecfg;
  mmfile_t minus, plus;
  struct diff_words_style *style = diff_words->style;

  struct diff_options *opt = diff_words->opt;
  const char *line_prefix;

  assert(opt);
  line_prefix = diff_line_prefix(opt);

  /* special case: only removal */
  if (!diff_words->plus.text.size) {
    emit_diff_symbol(diff_words->opt, DIFF_SYMBOL_WORD_DIFF,
         line_prefix, strlen(line_prefix), 0);
    fn_out_diff_words_write_helper(diff_words->opt,
      &style->old_word, style->newline,
      diff_words->minus.text.size,
      diff_words->minus.text.ptr);
    diff_words->minus.text.size = 0;
    return;
  }

  diff_words->current_plus = diff_words->plus.text.ptr;
  diff_words->last_minus = 0;

  memset(&xpp, 0, sizeof(xpp));
  memset(&xecfg, 0, sizeof(xecfg));
  diff_words_fill(&diff_words->minus, &minus, diff_words->word_regex);
  diff_words_fill(&diff_words->plus, &plus, diff_words->word_regex);
  xpp.flags = 0;
  /* as only the hunk header will be parsed, we need a 0-context */
  xecfg.ctxlen = 0;
  if (xdi_diff_outf(&minus, &plus, fn_out_diff_words_aux, NULL,
        diff_words, &xpp, &xecfg))
    die("unable to generate word diff");
  free(minus.ptr);
  free(plus.ptr);
  if (diff_words->current_plus != diff_words->plus.text.ptr +
      diff_words->plus.text.size) {
    if (color_words_output_graph_prefix(diff_words))
      emit_diff_symbol(diff_words->opt, DIFF_SYMBOL_WORD_DIFF,
           line_prefix, strlen(line_prefix), 0);
    fn_out_diff_words_write_helper(diff_words->opt,
      &style->ctx, style->newline,
      diff_words->plus.text.ptr + diff_words->plus.text.size
      - diff_words->current_plus, diff_words->current_plus);
  }
  diff_words->minus.text.size = diff_words->plus.text.size = 0;
}

/* In "color-words" mode, show word-diff of words accumulated in the buffer */
static void diff_words_flush(struct emit_callback *ecbdata)
{
  struct diff_options *wo = ecbdata->diff_words->opt;

  if (ecbdata->diff_words->minus.text.size ||
      ecbdata->diff_words->plus.text.size)
    diff_words_show(ecbdata->diff_words);

  if (wo->emitted_symbols) {
    struct diff_options *o = ecbdata->opt;
    struct emitted_diff_symbols *wol = wo->emitted_symbols;
    int i;

    /*
     * NEEDSWORK:
     * Instead of appending each, concat all words to a line?
     */
    for (i = 0; i < wol->nr; i++)
      append_emitted_diff_symbol(o, &wol->buf[i]);

    for (i = 0; i < wol->nr; i++)
      free((void *)wol->buf[i].line);

    wol->nr = 0;
  }
}

static void diff_filespec_load_driver(struct diff_filespec *one,
              struct index_state *istate)
{
  /* Use already-loaded driver */
  if (one->driver)
    return;

  if (S_ISREG(one->mode))
    one->driver = userdiff_find_by_path(istate, one->path);

  /* Fallback to default settings */
  if (!one->driver)
    one->driver = userdiff_find_by_name("default");
}

static const char *userdiff_word_regex(struct diff_filespec *one,
               struct index_state *istate)
{
  diff_filespec_load_driver(one, istate);
  return one->driver->word_regex;
}

static void init_diff_words_data(struct emit_callback *ecbdata,
         struct diff_options *orig_opts,
         struct diff_filespec *one,
         struct diff_filespec *two)
{
  int i;
  struct diff_options *o = xmalloc(sizeof(struct diff_options));
  memcpy(o, orig_opts, sizeof(struct diff_options));

  CALLOC_ARRAY(ecbdata->diff_words, 1);
  ecbdata->diff_words->type = o->word_diff;
  ecbdata->diff_words->opt = o;

  if (orig_opts->emitted_symbols)
    CALLOC_ARRAY(o->emitted_symbols, 1);

  if (!o->word_regex)
    o->word_regex = userdiff_word_regex(one, o->repo->index);
  if (!o->word_regex)
    o->word_regex = userdiff_word_regex(two, o->repo->index);
  if (!o->word_regex)
    o->word_regex = diff_word_regex_cfg;
  if (o->word_regex) {
    ecbdata->diff_words->word_regex = (regex_t *)
      xmalloc(sizeof(regex_t));
    if (regcomp(ecbdata->diff_words->word_regex,
          o->word_regex,
          REG_EXTENDED | REG_NEWLINE))
      die("invalid regular expression: %s",
          o->word_regex);
  }
  for (i = 0; i < ARRAY_SIZE(diff_words_styles); i++) {
    if (o->word_diff == diff_words_styles[i].type) {
      ecbdata->diff_words->style =
        &diff_words_styles[i];
      break;
    }
  }
  if (want_color(o->use_color)) {
    struct diff_words_style *st = ecbdata->diff_words->style;
    st->old_word.color = diff_get_color_opt(o, DIFF_FILE_OLD);
    st->new_word.color = diff_get_color_opt(o, DIFF_FILE_NEW);
    st->ctx.color = diff_get_color_opt(o, DIFF_CONTEXT);
  }
}

static void free_diff_words_data(struct emit_callback *ecbdata)
{
  if (ecbdata->diff_words) {
    diff_words_flush(ecbdata);
    free_emitted_diff_symbols(ecbdata->diff_words->opt->emitted_symbols);
    free (ecbdata->diff_words->opt);
    free (ecbdata->diff_words->minus.text.ptr);
    free (ecbdata->diff_words->minus.orig);
    free (ecbdata->diff_words->plus.text.ptr);
    free (ecbdata->diff_words->plus.orig);
    if (ecbdata->diff_words->word_regex) {
      regfree(ecbdata->diff_words->word_regex);
      free(ecbdata->diff_words->word_regex);
    }
    FREE_AND_NULL(ecbdata->diff_words);
  }
}

const char *diff_get_color(enum git_colorbool diff_use_color, enum color_diff ix)
{
  if (want_color(diff_use_color))
    return diff_colors[ix];
  return "";
}

const char *diff_line_prefix(struct diff_options *opt)
{
  return opt->output_prefix ?
    opt->output_prefix(opt, opt->output_prefix_data) :
    "";
}

static unsigned long sane_truncate_line(char *line, unsigned long len)
{
  const char *cp;
  unsigned long allot;
  size_t l = len;

  cp = line;
  allot = l;
  while (0 < l) {
    (void) utf8_width(&cp, &l);
    if (!cp)
      break; /* truncated in the middle? */
  }
  return allot - l;
}

static void find_lno(const char *line, struct emit_callback *ecbdata)
{
  const char *p;
  ecbdata->lno_in_preimage = 0;
  ecbdata->lno_in_postimage = 0;
  p = strchr(line, '-');
  if (!p)
    return; /* cannot happen */
  ecbdata->lno_in_preimage = strtol(p + 1, NULL, 10);
  p = strchr(p, '+');
  if (!p)
    return; /* cannot happen */
  ecbdata->lno_in_postimage = strtol(p + 1, NULL, 10);
}

static int fn_out_consume(void *priv, char *line, unsigned long len)
{
  struct emit_callback *ecbdata = priv;
  struct diff_options *o = ecbdata->opt;

  o->found_changes = 1;

  if (ecbdata->header) {
    emit_diff_symbol(o, DIFF_SYMBOL_HEADER,
         ecbdata->header->buf, ecbdata->header->len, 0);
    strbuf_reset(ecbdata->header);
    ecbdata->header = NULL;
  }

  if (ecbdata->label_path[0]) {
    emit_diff_symbol(o, DIFF_SYMBOL_FILEPAIR_MINUS,
         ecbdata->label_path[0],
         strlen(ecbdata->label_path[0]), 0);
    emit_diff_symbol(o, DIFF_SYMBOL_FILEPAIR_PLUS,
         ecbdata->label_path[1],
         strlen(ecbdata->label_path[1]), 0);
    ecbdata->label_path[0] = ecbdata->label_path[1] = NULL;
  }

  if (line[0] == '@') {
    if (ecbdata->diff_words)
      diff_words_flush(ecbdata);
    len = sane_truncate_line(line, len);
    find_lno(line, ecbdata);
    emit_hunk_header(ecbdata, line, len);
    return 0;
  }

  if (ecbdata->diff_words) {
    enum diff_symbol s =
      ecbdata->diff_words->type == DIFF_WORDS_PORCELAIN ?
      DIFF_SYMBOL_WORDS_PORCELAIN : DIFF_SYMBOL_WORDS;
    if (line[0] == '-') {
      diff_words_append(line, len,
            &ecbdata->diff_words->minus);
      return 0;
    } else if (line[0] == '+') {
      diff_words_append(line, len,
            &ecbdata->diff_words->plus);
      return 0;
    } else if (starts_with(line, "\\ ")) {
      /*
       * Eat the "no newline at eof" marker as if we
       * saw a "+" or "-" line with nothing on it,
       * and return without diff_words_flush() to
       * defer processing. If this is the end of
       * preimage, more "+" lines may come after it.
       */
      return 0;
    }
    diff_words_flush(ecbdata);
    emit_diff_symbol(o, s, line, len, 0);
    return 0;
  }

  switch (line[0]) {
  case '+':
    ecbdata->lno_in_postimage++;
    emit_add_line(ecbdata, line + 1, len - 1);
    break;
  case '-':
    ecbdata->lno_in_preimage++;
    emit_del_line(ecbdata, line + 1, len - 1);
    break;
  case ' ':
    ecbdata->lno_in_postimage++;
    ecbdata->lno_in_preimage++;
    emit_context_line(ecbdata, line + 1, len - 1);
    break;
  case '\\':
    /* incomplete line at the end */
    switch (ecbdata->last_line_kind) {
    case '+':
    case '-':
    case ' ':
      break;
    default:
      BUG("fn_out_consume: '\\No newline' after unknown line (%c)",
          ecbdata->last_line_kind);
    }
    ecbdata->lno_in_preimage++;
    emit_incomplete_line_marker(ecbdata, line, len);
    break;
  default:
    BUG("fn_out_consume: unknown line '%s'", line);
  }
  ecbdata->last_line_kind = line[0];
  return 0;
}

static int quick_consume(void *priv, char *line UNUSED, unsigned long len UNUSED)
{
  struct emit_callback *ecbdata = priv;
  struct diff_options *o = ecbdata->opt;

  o->found_changes = 1;
  return 1;
}

static void discard_pending_rm(struct line_range_callback *s)
{
  strbuf_reset(&s->pending_rm);
  s->pending_rm_count = 0;
}

static void flush_rhunk(struct line_range_callback *s)
{
  struct strbuf hdr = STRBUF_INIT;
  const char *p, *end;

  if (!s->rhunk_active || s->ret)
    return;

  /* Drain any pending removal lines into the range hunk */
  if (s->pending_rm_count) {
    strbuf_addbuf(&s->rhunk, &s->pending_rm);
    s->rhunk_old_count += s->pending_rm_count;
    s->rhunk_has_changes = 1;
    discard_pending_rm(s);
  }

  /*
   * Suppress context-only hunks: they contain no actual changes
   * and would just be noise.  This can happen when the inflated
   * ctxlen causes xdiff to emit context covering a range that
   * has no changes in this commit.
   */
  if (!s->rhunk_has_changes) {
    s->rhunk_active = 0;
    strbuf_reset(&s->rhunk);
    return;
  }

  strbuf_addf(&hdr, "@@ -%ld,%ld +%ld,%ld @@",
        s->rhunk_old_begin, s->rhunk_old_count,
        s->rhunk_new_begin, s->rhunk_new_count);
  if (s->funclen > 0) {
    strbuf_addch(&hdr, ' ');
    strbuf_add(&hdr, s->func, s->funclen);
  }
  strbuf_addch(&hdr, '\n');

  s->ret = s->orig_line_fn(s->orig_cb_data, hdr.buf, hdr.len);
  strbuf_release(&hdr);

  /*
   * Replay buffered lines one at a time through fn_out_consume.
   * The cast discards const because xdiff_emit_line_fn takes
   * char *, though fn_out_consume does not modify the buffer.
   */
  p = s->rhunk.buf;
  end = p + s->rhunk.len;
  while (!s->ret && p < end) {
    const char *eol = memchr(p, '\n', end - p);
    unsigned long line_len = eol ? (unsigned long)(eol - p + 1)
               : (unsigned long)(end - p);
    s->ret = s->orig_line_fn(s->orig_cb_data, (char *)p, line_len);
    p += line_len;
  }

  s->rhunk_active = 0;
  strbuf_reset(&s->rhunk);
}

static void line_range_hunk_fn(void *data,
             long old_begin, long old_nr UNUSED,
             long new_begin, long new_nr UNUSED,
             const char *func, long funclen)
{
  struct line_range_callback *s = data;

  /*
   * When count > 0, begin is 1-based.  When count == 0, begin is
   * adjusted down by 1 by xdl_emit_hunk_hdr(), but no lines of
   * that type will arrive, so the value is unused.
   *
   * Any pending removal lines from the previous xdiff hunk are
   * intentionally left in pending_rm: the line callback will
   * flush or discard them when the next content line reveals
   * whether the removals precede in-range content.
   */
  s->lno_post = new_begin;
  s->lno_pre = old_begin;

  if (funclen > 0) {
    if (funclen > (long)sizeof(s->func))
      funclen = sizeof(s->func);
    memcpy(s->func, func, funclen);
  }
  s->funclen = funclen;
}

static int line_range_line_fn(void *priv, char *line, unsigned long len)
{
  struct line_range_callback *s = priv;
  const struct range *cur;
  long lno_0, cur_pre;

  if (s->ret)
    return s->ret;

  if (line[0] == '-') {
    if (!s->pending_rm_count)
      s->pending_rm_pre_begin = s->lno_pre;
    s->lno_pre++;
    strbuf_add(&s->pending_rm, line, len);
    s->pending_rm_count++;
    return s->ret;
  }

  if (line[0] == '\\') {
    if (s->pending_rm_count)
      strbuf_add(&s->pending_rm, line, len);
    else if (s->rhunk_active)
      strbuf_add(&s->rhunk, line, len);
    /* otherwise outside tracked range; drop silently */
    return s->ret;
  }

  if (line[0] != '+' && line[0] != ' ')
    BUG("unexpected diff line type '%c'", line[0]);

  lno_0 = s->lno_post - 1;
  cur_pre = s->lno_pre; /* save before advancing for context lines */
  s->lno_post++;
  if (line[0] == ' ')
    s->lno_pre++;

  /* Advance past ranges we've passed */
  while (s->cur_range < s->ranges->nr &&
         lno_0 >= s->ranges->ranges[s->cur_range].end) {
    if (s->rhunk_active)
      flush_rhunk(s);
    discard_pending_rm(s);
    s->cur_range++;
  }

  /* Past all ranges */
  if (s->cur_range >= s->ranges->nr) {
    discard_pending_rm(s);
    return s->ret;
  }

  cur = &s->ranges->ranges[s->cur_range];

  /* Before current range */
  if (lno_0 < cur->start) {
    discard_pending_rm(s);
    return s->ret;
  }

  /* In range so start a new range hunk if needed */
  if (!s->rhunk_active) {
    s->rhunk_active = 1;
    s->rhunk_has_changes = 0;
    s->rhunk_new_begin = lno_0 + 1;
    s->rhunk_old_begin = s->pending_rm_count
      ? s->pending_rm_pre_begin : cur_pre;
    s->rhunk_old_count = 0;
    s->rhunk_new_count = 0;
    strbuf_reset(&s->rhunk);
  }

  /* Flush pending removals into range hunk */
  if (s->pending_rm_count) {
    strbuf_addbuf(&s->rhunk, &s->pending_rm);
    s->rhunk_old_count += s->pending_rm_count;
    s->rhunk_has_changes = 1;
    discard_pending_rm(s);
  }

  strbuf_add(&s->rhunk, line, len);
  s->rhunk_new_count++;
  if (line[0] == '+')
    s->rhunk_has_changes = 1;
  else
    s->rhunk_old_count++;

  return s->ret;
}

static void pprint_rename(struct strbuf *name, const char *a, const char *b)
{
  const char *old_name = a;
  const char *new_name = b;
  int pfx_length, sfx_length;
  int pfx_adjust_for_slash;
  int len_a = strlen(a);
  int len_b = strlen(b);
  int a_midlen, b_midlen;
  int qlen_a = quote_c_style(a, NULL, NULL, 0);
  int qlen_b = quote_c_style(b, NULL, NULL, 0);

  if (qlen_a || qlen_b) {
    quote_c_style(a, name, NULL, 0);
    strbuf_addstr(name, " => ");
    quote_c_style(b, name, NULL, 0);
    return;
  }

  /* Find common prefix */
  pfx_length = 0;
  while (*old_name && *new_name && *old_name == *new_name) {
    if (*old_name == '/')
      pfx_length = old_name - a + 1;
    old_name++;
    new_name++;
  }

  /* Find common suffix */
  old_name = a + len_a;
  new_name = b + len_b;
  sfx_length = 0;
  /*
   * If there is a common prefix, it must end in a slash.  In
   * that case we let this loop run 1 into the prefix to see the
   * same slash.
   *
   * If there is no common prefix, we cannot do this as it would
   * underrun the input strings.
   */
  pfx_adjust_for_slash = (pfx_length ? 1 : 0);
  while (a + pfx_length - pfx_adjust_for_slash <= old_name &&
         b + pfx_length - pfx_adjust_for_slash <= new_name &&
         *old_name == *new_name) {
    if (*old_name == '/')
      sfx_length = len_a - (old_name - a);
    old_name--;
    new_name--;
  }

  /*
   * pfx{mid-a => mid-b}sfx
   * {pfx-a => pfx-b}sfx
   * pfx{sfx-a => sfx-b}
   * name-a => name-b
   */
  a_midlen = len_a - pfx_length - sfx_length;
  b_midlen = len_b - pfx_length - sfx_length;
  if (a_midlen < 0)
    a_midlen = 0;
  if (b_midlen < 0)
    b_midlen = 0;

  strbuf_grow(name, pfx_length + a_midlen + b_midlen + sfx_length + 7);
  if (pfx_length + sfx_length) {
    strbuf_add(name, a, pfx_length);
    strbuf_addch(name, '{');
  }
  strbuf_add(name, a + pfx_length, a_midlen);
  strbuf_addstr(name, " => ");
  strbuf_add(name, b + pfx_length, b_midlen);
  if (pfx_length + sfx_length) {
    strbuf_addch(name, '}');
    strbuf_add(name, a + len_a - sfx_length, sfx_length);
  }
}

static struct diffstat_file *diffstat_add(struct diffstat_t *diffstat,
            const char *name_a,
            const char *name_b)
{
  struct diffstat_file *x;
  CALLOC_ARRAY(x, 1);
  ALLOC_GROW(diffstat->files, diffstat->nr + 1, diffstat->alloc);
  diffstat->files[diffstat->nr++] = x;
  if (name_b) {
    x->from_name = xstrdup(name_a);
    x->name = xstrdup(name_b);
    x->is_renamed = 1;
  }
  else {
    x->from_name = NULL;
    x->name = xstrdup(name_a);
  }
  return x;
}

static int diffstat_consume(void *priv, char *line, unsigned long len)
{
  struct diffstat_t *diffstat = priv;
  struct diffstat_file *x = diffstat->files[diffstat->nr - 1];

  if (!len)
    BUG("xdiff fed us an empty line");

  if (line[0] == '+')
    x->added++;
  else if (line[0] == '-')
    x->deleted++;
  return 0;
}

const char mime_boundary_leader[] = "------------";

static int scale_linear(int it, int width, int max_change)
{
  if (!it)
    return 0;
  /*
   * make sure that at least one '-' or '+' is printed if
   * there is any change to this path. The easiest way is to
   * scale linearly as if the allotted width is one column shorter
   * than it is, and then add 1 to the result.
   */
  return 1 + (it * (width - 1) / max_change);
}

static void show_graph(struct strbuf *out, char ch, int cnt,
           const char *set, const char *reset)
{
  if (cnt <= 0)
    return;
  strbuf_addstr(out, set);
  strbuf_addchars(out, ch, cnt);
  strbuf_addstr(out, reset);
}

static void fill_print_name(struct diffstat_file *file)
{
  struct strbuf pname = STRBUF_INIT;

  if (file->print_name)
    return;

  if (file->is_renamed)
    pprint_rename(&pname, file->from_name, file->name);
  else
    quote_c_style(file->name, &pname, NULL, 0);

  if (file->comments)
    strbuf_addf(&pname, " (%s)", file->comments);

  file->print_name = strbuf_detach(&pname, NULL);
}

static void print_stat_summary_inserts_deletes(struct diff_options *options,
    int files, int insertions, int deletions)
{
  struct strbuf sb = STRBUF_INIT;

  if (!files) {
    assert(insertions == 0 && deletions == 0);
    emit_diff_symbol(options, DIFF_SYMBOL_STATS_SUMMARY_NO_FILES,
         NULL, 0, 0);
    return;
  }

  strbuf_addf(&sb,
        (files == 1) ? " %d file changed" : " %d files changed",
        files);

  /*
   * For binary diff, the caller may want to print "x files
   * changed" with insertions == 0 && deletions == 0.
   *
   * Not omitting "0 insertions(+), 0 deletions(-)" in this case
   * is probably less confusing (i.e skip over "2 files changed
   * but nothing about added/removed lines? Is this a bug in Git?").
   */
  if (insertions || deletions == 0) {
    strbuf_addf(&sb,
          (insertions == 1) ? ", %d insertion(+)" : ", %d insertions(+)",
          insertions);
  }

  if (deletions || insertions == 0) {
    strbuf_addf(&sb,
          (deletions == 1) ? ", %d deletion(-)" : ", %d deletions(-)",
          deletions);
  }
  strbuf_addch(&sb, '\n');
  emit_diff_symbol(options, DIFF_SYMBOL_STATS_SUMMARY_INSERTS_DELETES,
       sb.buf, sb.len, 0);
  strbuf_release(&sb);
}

void print_stat_summary(FILE *fp, int files,
      int insertions, int deletions)
{
  struct diff_options o;
  memset(&o, 0, sizeof(o));
  o.file = fp;

  print_stat_summary_inserts_deletes(&o, files, insertions, deletions);
}

/*
 * Like utf8_width(), but guaranteed safe for use in loops that subtract
 * per-character widths:
 *
 *   - utf8_width() sets *start to NULL on invalid UTF-8 and returns 0;
 *     we restore the pointer and advance by one byte, returning width 1
 *     (matching the strlen()-based fallback in utf8_strwidth()).
 *
 *   - utf8_width() returns -1 for control characters; we return 0
 *     (matching utf8_strnwidth() which skips them).
 */
static int utf8_ish_width(const char **start)
{
  const char *old = *start;
  int w = utf8_width(start, NULL);
  if (!*start) {
    *start = old + 1;
    return 1;
  }
  return (w < 0) ? 0 : w;
}

static void show_stats(struct diffstat_t *data, struct diff_options *options)
{
  int i, len, add, del, adds = 0, dels = 0;
  uintmax_t max_change = 0, max_len = 0;
  int total_files = data->nr, count;
  int width, name_width, graph_width, number_width = 0, bin_width = 0;
  const char *reset, *add_c, *del_c;
  int extra_shown = 0;
  const char *line_prefix = diff_line_prefix(options);
  struct strbuf out = STRBUF_INIT;

  if (data->nr == 0)
    return;

  count = options->stat_count ? options->stat_count : data->nr;

  reset = diff_get_color_opt(options, DIFF_RESET);
  add_c = diff_get_color_opt(options, DIFF_FILE_NEW);
  del_c = diff_get_color_opt(options, DIFF_FILE_OLD);

  /*
   * Find the longest filename and max number of changes
   */
  for (i = 0; (i < count) && (i < data->nr); i++) {
    struct diffstat_file *file = data->files[i];
    uintmax_t change = file->added + file->deleted;

    if (!file->is_interesting && (change == 0)) {
      count++; /* not shown == room for one more */
      continue;
    }
    fill_print_name(file);
    len = utf8_strwidth(file->print_name);
    if (max_len < len)
      max_len = len;

    if (file->is_unmerged) {
      /* "Unmerged" is 8 characters */
      bin_width = bin_width < 8 ? 8 : bin_width;
      continue;
    }
    if (file->is_binary) {
      /* "Bin XXX -> YYY bytes" */
      int w = 14 + decimal_width(file->added)
        + decimal_width(file->deleted);
      bin_width = bin_width < w ? w : bin_width;
      /* Display change counts aligned with "Bin" */
      number_width = 3;
      continue;
    }

    if (max_change < change)
      max_change = change;
  }
  count = i; /* where we can stop scanning in data->files[] */

  /*
   * We have width = stat_width or term_columns() columns total minus the
   * length of line_prefix skipping ANSI escape codes to get the display
   * width (e.g., skip ANSI-colored strings in "log --graph --stat").
   * We want a maximum of min(max_len, stat_name_width) for the name part.
   * We want a maximum of min(max_change, stat_graph_width) for the +- part.
   * We also need 1 for " " and 4 + decimal_width(max_change)
   * for " | NNNN " and one the empty column at the end, altogether
   * 6 + decimal_width(max_change).
   *
   * If there's not enough space, we will use the smaller of
   * stat_name_width (if set) and 5/8*width for the filename,
   * and the rest for constant elements + graph part, but no more
   * than stat_graph_width for the graph part.
   * (5/8 gives 50 for filename and 30 for the constant parts + graph
   * for the standard terminal size).
   *
   * In other words: stat_width limits the maximum width, and
   * stat_name_width fixes the maximum width of the filename,
   * and is also used to divide available columns if there
   * aren't enough.
   *
   * Binary files are displayed with "Bin XXX -> YYY bytes"
   * instead of the change count and graph. This part is treated
   * similarly to the graph part, except that it is not
   * "scaled". If total width is too small to accommodate the
   * guaranteed minimum width of the filename part and the
   * separators and this message, this message will "overflow"
   * making the line longer than the maximum width.
   */
  if (options->stat_width == -1)
    width = term_columns() - utf8_strnwidth(line_prefix, strlen(line_prefix), 1);
  else
    width = options->stat_width ? options->stat_width : 80;
  number_width = decimal_width(max_change) > number_width ?
    decimal_width(max_change) : number_width;

  if (options->stat_name_width == -1)
    options->stat_name_width = diff_stat_name_width;
  if (options->stat_graph_width == -1)
    options->stat_graph_width = diff_stat_graph_width;

  /*
   * Guarantee 3/8*16 == 6 for the graph part
   * and 5/8*16 == 10 for the filename part
   */
  if (width < 16 + 6 + number_width)
    width = 16 + 6 + number_width;

  /*
   * First assign sizes that are wanted, ignoring available width.
   * strlen("Bin XXX -> YYY bytes") == bin_width, and the part
   * starting from "XXX" should fit in graph_width.
   */
  graph_width = max_change + 4 > bin_width ? max_change : bin_width - 4;
  if (options->stat_graph_width &&
      options->stat_graph_width < graph_width)
    graph_width = options->stat_graph_width;

  name_width = (options->stat_name_width > 0 &&
          options->stat_name_width < max_len) ?
    options->stat_name_width : max_len;

  /*
   * Adjust adjustable widths not to exceed maximum width
   */
  if (name_width + number_width + 6 + graph_width > width) {
    if (graph_width > width * 3/8 - number_width - 6) {
      graph_width = width * 3/8 - number_width - 6;
      if (graph_width < 6)
        graph_width = 6;
    }

    if (options->stat_graph_width &&
        graph_width > options->stat_graph_width)
      graph_width = options->stat_graph_width;
    if (name_width > width - number_width - 6 - graph_width)
      name_width = width - number_width - 6 - graph_width;
    else
      graph_width = width - number_width - 6 - name_width;
  }

  /*
   * From here name_width is the width of the name area,
   * and graph_width is the width of the graph area.
   * max_change is used to scale graph properly.
   */
  for (i = 0; i < count; i++) {
    const char *prefix = "";
    struct diffstat_file *file = data->files[i];
    char *name = file->print_name;
    uintmax_t added = file->added;
    uintmax_t deleted = file->deleted;
    int name_len, padding;

    if (!file->is_interesting && (added + deleted == 0))
      continue;

    /*
     * "scale" the filename
     */
    len = name_width;
    name_len = utf8_strwidth(name);
    if (name_width < name_len) {
      char *slash;
      prefix = "...";
      len -= 3;
      if (len < 0)
        len = 0;

      while (name_len > len && *name)
        name_len -= utf8_ish_width((const char**)&name);

      slash = strchr(name, '/');
      if (slash)
        name = slash;
    }
    padding = len - utf8_strwidth(name);
    if (padding < 0)
      padding = 0;

    if (file->is_binary) {
      strbuf_addf(&out, " %s%s%*s | %*s",
            prefix, name, padding, "",
            number_width, "Bin");
      if (!added && !deleted) {
        strbuf_addch(&out, '\n');
        emit_diff_symbol(options, DIFF_SYMBOL_STATS_LINE,
             out.buf, out.len, 0);
        strbuf_reset(&out);
        continue;
      }
      strbuf_addf(&out, " %s%"PRIuMAX"%s",
        del_c, deleted, reset);
      strbuf_addstr(&out, " -> ");
      strbuf_addf(&out, "%s%"PRIuMAX"%s",
        add_c, added, reset);
      strbuf_addstr(&out, " bytes\n");
      emit_diff_symbol(options, DIFF_SYMBOL_STATS_LINE,
           out.buf, out.len, 0);
      strbuf_reset(&out);
      continue;
    }
    else if (file->is_unmerged) {
      strbuf_addf(&out, " %s%s%*s | %*s",
            prefix, name, padding, "",
            number_width, "Unmerged\n");
      emit_diff_symbol(options, DIFF_SYMBOL_STATS_LINE,
           out.buf, out.len, 0);
      strbuf_reset(&out);
      continue;
    }

    /*
     * scale the add/delete
     */
    add = added;
    del = deleted;

    if (graph_width <= max_change) {
      int total = scale_linear(add + del, graph_width, max_change);
      if (total < 2 && add && del)
        /* width >= 2 due to the sanity check */
        total = 2;
      if (add < del) {
        add = scale_linear(add, graph_width, max_change);
        del = total - add;
      } else {
        del = scale_linear(del, graph_width, max_change);
        add = total - del;
      }
    }
    strbuf_addf(&out, " %s%s%*s | %*"PRIuMAX"%s",
          prefix, name, padding, "",
          number_width, added + deleted,
          added + deleted ? " " : "");
    show_graph(&out, '+', add, add_c, reset);
    show_graph(&out, '-', del, del_c, reset);
    strbuf_addch(&out, '\n');
    emit_diff_symbol(options, DIFF_SYMBOL_STATS_LINE,
         out.buf, out.len, 0);
    strbuf_reset(&out);
  }

  for (i = 0; i < data->nr; i++) {
    struct diffstat_file *file = data->files[i];
    uintmax_t added = file->added;
    uintmax_t deleted = file->deleted;

    if (file->is_unmerged ||
        (!file->is_interesting && (added + deleted == 0))) {
      total_files--;
      continue;
    }

    if (!file->is_binary) {
      adds += added;
      dels += deleted;
    }
    if (i < count)
      continue;
    if (!extra_shown)
      emit_diff_symbol(options,
           DIFF_SYMBOL_STATS_SUMMARY_ABBREV,
           NULL, 0, 0);
    extra_shown = 1;
  }

  print_stat_summary_inserts_deletes(options, total_files, adds, dels);
  strbuf_release(&out);
}

static void show_shortstats(struct diffstat_t *data, struct diff_options *options)
{
  int i, adds = 0, dels = 0, total_files = data->nr;

  if (data->nr == 0)
    return;

  for (i = 0; i < data->nr; i++) {
    int added = data->files[i]->added;
    int deleted = data->files[i]->deleted;

    if (data->files[i]->is_unmerged ||
        (!data->files[i]->is_interesting && (added + deleted == 0))) {
      total_files--;
    } else if (!data->files[i]->is_binary) { /* don't count bytes */
      adds += added;
      dels += deleted;
    }
  }
  print_stat_summary_inserts_deletes(options, total_files, adds, dels);
}

static void show_numstat(struct diffstat_t *data, struct diff_options *options)
{
  int i;

  if (data->nr == 0)
    return;

  for (i = 0; i < data->nr; i++) {
    struct diffstat_file *file = data->files[i];

    fprintf(options->file, "%s", diff_line_prefix(options));

    if (file->is_binary)
      fprintf(options->file, "-\t-\t");
    else
      fprintf(options->file,
        "%"PRIuMAX"\t%"PRIuMAX"\t",
        file->added, file->deleted);
    if (options->line_termination) {
      fill_print_name(file);
      if (!file->is_renamed)
        write_name_quoted(file->name, options->file,
              options->line_termination);
      else {
        fputs(file->print_name, options->file);
        putc(options->line_termination, options->file);
      }
    } else {
      if (file->is_renamed) {
        putc('\0', options->file);
        write_name_quoted(file->from_name, options->file, '\0');
      }
      write_name_quoted(file->name, options->file, '\0');
    }
  }
}

struct dirstat_file {
  const char *name;
  unsigned long changed;
};

struct dirstat_dir {
  struct dirstat_file *files;
  int alloc, nr, permille, cumulative;
};

static long gather_dirstat(struct diff_options *opt, struct dirstat_dir *dir,
    unsigned long changed, const char *base, int baselen)
{
  unsigned long sum_changes = 0;
  unsigned int sources = 0;
  const char *line_prefix = diff_line_prefix(opt);

  while (dir->nr) {
    struct dirstat_file *f = dir->files;
    int namelen = strlen(f->name);
    unsigned long changes;
    const char *slash;

    if (namelen < baselen)
      break;
    if (memcmp(f->name, base, baselen))
      break;
    slash = strchr(f->name + baselen, '/');
    if (slash) {
      int newbaselen = slash + 1 - f->name;
      changes = gather_dirstat(opt, dir, changed, f->name, newbaselen);
      sources++;
    } else {
      changes = f->changed;
      dir->files++;
      dir->nr--;
      sources += 2;
    }
    sum_changes += changes;
  }

  /*
   * We don't report dirstat's for
   *  - the top level
   *  - or cases where everything came from a single directory
   *    under this directory (sources == 1).
   */
  if (baselen && sources != 1) {
    if (sum_changes) {
      int permille = sum_changes * 1000 / changed;
      if (permille >= dir->permille) {
        fprintf(opt->file, "%s%4d.%01d%% %.*s\n", line_prefix,
          permille / 10, permille % 10, baselen, base);
        if (!dir->cumulative)
          return 0;
      }
    }
  }
  return sum_changes;
}

static int dirstat_compare(const void *_a, const void *_b)
{
  const struct dirstat_file *a = _a;
  const struct dirstat_file *b = _b;
  return strcmp(a->name, b->name);
}

static void conclude_dirstat(struct diff_options *options,
           struct dirstat_dir *dir,
           unsigned long changed)
{
  struct dirstat_file *to_free = dir->files;

  if (!changed) {
    /* This can happen even with many files, if everything was renames */
    ;
  } else {
    /* Show all directories with more than x% of the changes */
    QSORT(dir->files, dir->nr, dirstat_compare);
    gather_dirstat(options, dir, changed, "", 0);
  }

  free(to_free);
}

static void show_dirstat(struct diff_options *options)
{
  int i;
  unsigned long changed;
  struct dirstat_dir dir;
  struct diff_queue_struct *q = &diff_queued_diff;

  dir.files = NULL;
  dir.alloc = 0;
  dir.nr = 0;
  dir.permille = options->dirstat_permille;
  dir.cumulative = options->flags.dirstat_cumulative;

  changed = 0;
  for (i = 0; i < q->nr; i++) {
    struct diff_filepair *p = q->queue[i];
    const char *name;
    unsigned long copied, added, damage;
    struct diff_populate_filespec_options dpf_options = {
      .check_size_only = 1,
    };

    name = p->two->path ? p->two->path : p->one->path;

    if (p->one->oid_valid && p->two->oid_valid &&
        oideq(&p->one->oid, &p->two->oid)) {
      /*
       * The SHA1 has not changed, so pre-/post-content is
       * identical. We can therefore skip looking at the
       * file contents altogether.
       */
      damage = 0;
      goto found_damage;
    }

    if (options->flags.dirstat_by_file) {
      /*
       * In --dirstat-by-file mode, we don't really need to
       * look at the actual file contents at all.
       * The fact that the SHA1 changed is enough for us to
       * add this file to the list of results
       * (with each file contributing equal damage).
       */
      damage = 1;
      goto found_damage;
    }

    if (DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two)) {
      diff_populate_filespec(options->repo, p->one, NULL);
      diff_populate_filespec(options->repo, p->two, NULL);
      diffcore_count_changes(options->repo,
                 p->one, p->two, NULL, NULL,
                 &copied, &added);
      diff_free_filespec_data(p->one);
      diff_free_filespec_data(p->two);
    } else if (DIFF_FILE_VALID(p->one)) {
      diff_populate_filespec(options->repo, p->one, &dpf_options);
      copied = added = 0;
      diff_free_filespec_data(p->one);
    } else if (DIFF_FILE_VALID(p->two)) {
      diff_populate_filespec(options->repo, p->two, &dpf_options);
      copied = 0;
      added = p->two->size;
      diff_free_filespec_data(p->two);
    } else
      continue;

    /*
     * Original minus copied is the removed material,
     * added is the new material.  They are both damages
     * made to the preimage.
     * If the resulting damage is zero, we know that
     * diffcore_count_changes() considers the two entries to
     * be identical, but since the oid changed, we
     * know that there must have been _some_ kind of change,
     * so we force all entries to have damage > 0.
     */
    damage = (p->one->size - copied) + added;
    if (!damage)
      damage = 1;

found_damage:
    ALLOC_GROW(dir.files, dir.nr + 1, dir.alloc);
    dir.files[dir.nr].name = name;
    dir.files[dir.nr].changed = damage;
    changed += damage;
    dir.nr++;
  }

  conclude_dirstat(options, &dir, changed);
}

static void show_dirstat_by_line(struct diffstat_t *data, struct diff_options *options)
{
  int i;
  unsigned long changed;
  struct dirstat_dir dir;

  if (data->nr == 0)
    return;

  dir.files = NULL;
  dir.alloc = 0;
  dir.nr = 0;
  dir.permille = options->dirstat_permille;
  dir.cumulative = options->flags.dirstat_cumulative;

  changed = 0;
  for (i = 0; i < data->nr; i++) {
    struct diffstat_file *file = data->files[i];
    unsigned long damage = file->added + file->deleted;
    if (file->is_binary)
      /*
       * binary files counts bytes, not lines. Must find some
       * way to normalize binary bytes vs. textual lines.
       * The following heuristic assumes that there are 64
       * bytes per "line".
       * This is stupid and ugly, but very cheap...
       */
      damage = DIV_ROUND_UP(damage, 64);
    ALLOC_GROW(dir.files, dir.nr + 1, dir.alloc);
    dir.files[dir.nr].name = file->name;
    dir.files[dir.nr].changed = damage;
    changed += damage;
    dir.nr++;
  }

  conclude_dirstat(options, &dir, changed);
}

static void free_diffstat_file(struct diffstat_file *f)
{
  free(f->print_name);
  free(f->name);
  free(f->from_name);
  free(f);
}

void free_diffstat_info(struct diffstat_t *diffstat)
{
  int i;
  for (i = 0; i < diffstat->nr; i++)
    free_diffstat_file(diffstat->files[i]);
  free(diffstat->files);
}

struct checkdiff_t {
  const char *filename;
  int lineno;
  int conflict_marker_size;
  struct diff_options *o;
  unsigned ws_rule;
  unsigned status;
  int last_line_kind;
};

static void checkdiff_consume_hunk(void *priv,
           long ob UNUSED, long on UNUSED,
           long nb, long nn UNUSED,
           const char *func UNUSED, long funclen UNUSED)

{
  struct checkdiff_t *data = priv;
  data->lineno = nb - 1;
}

static int checkdiff_consume(void *priv, char *line, unsigned long len)
{
  struct checkdiff_t *data = priv;
  int last_line_kind;
  int marker_size = data->conflict_marker_size;
  const char *ws = diff_get_color(data->o->use_color, DIFF_WHITESPACE);
  const char *reset = diff_get_color(data->o->use_color, DIFF_RESET);
  const char *set = diff_get_color(data->o->use_color, DIFF_FILE_NEW);
  char *err;
  const char *line_prefix;

  assert(data->o);
  line_prefix = diff_line_prefix(data->o);

  last_line_kind = data->last_line_kind;
  data->last_line_kind = line[0];
  if (line[0] == '+') {
    unsigned bad;
    data->lineno++;
    if (is_conflict_marker_line(line + 1, len - 1, marker_size)) {
      data->status |= 1;
      fprintf(data->o->file,
        "%s%s:%d: leftover conflict marker\n",
        line_prefix, data->filename, data->lineno);
    }
    bad = ws_check(line + 1, len - 1, data->ws_rule);
    if (!bad)
      return 0;
    data->status |= bad;
    err = whitespace_error_string(bad);
    fprintf(data->o->file, "%s%s:%d: %s.\n",
      line_prefix, data->filename, data->lineno, err);
    free(err);
    emit_line(data->o, set, reset, line, 1);
    ws_check_emit(line + 1, len - 1, data->ws_rule,
            data->o->file, set, reset, ws);
  } else if (line[0] == ' ') {
    data->lineno++;
  } else if (line[0] == '\\') {
    /* no newline at the end of the line */
    if ((data->ws_rule & WS_INCOMPLETE_LINE) &&
        (last_line_kind == '+')) {
      unsigned bad = WS_INCOMPLETE_LINE;
      data->status |= bad;
      err = whitespace_error_string(bad);
      fprintf(data->o->file, "%s%s:%d: %s.\n",
        line_prefix, data->filename, data->lineno, err);
      free(err);
    }
  }
  return 0;
}

static unsigned char *deflate_it(char *data,
         unsigned long size,
         unsigned long *result_size)
{
  size_t bound;
  unsigned char *deflated;
  git_zstream stream;
  struct repo_config_values *cfg = repo_config_values(the_repository);

  git_deflate_init(&stream, cfg->zlib_compression_level);
  bound = git_deflate_bound(&stream, size);
  deflated = xmalloc(bound);
  stream.next_out = deflated;
  stream.avail_out = bound;

  stream.next_in = (unsigned char *)data;
  stream.avail_in = size;
  while (git_deflate(&stream, Z_FINISH) == Z_OK)
    ; /* nothing */
  git_deflate_end(&stream);
  *result_size = stream.total_out;
  return deflated;
}

static void emit_binary_diff_body(struct diff_options *o,
          mmfile_t *one, mmfile_t *two)
{
  void *cp;
  void *delta;
  void *deflated;
  void *data;
  unsigned long orig_size;
  unsigned long delta_size;
  unsigned long deflate_size;
  unsigned long data_size;

  /* We could do deflated delta, or we could do just deflated two,
   * whichever is smaller.
   */
  delta = NULL;
  deflated = deflate_it(two->ptr, two->size, &deflate_size);
  if (one->size && two->size) {
    size_t delta_size_st = 0;
    delta = diff_delta(one->ptr, one->size,
           two->ptr, two->size,
           &delta_size_st, deflate_size);
    delta_size = cast_size_t_to_ulong(delta_size_st);
    if (delta) {
      void *to_free = delta;
      orig_size = delta_size;
      delta = deflate_it(delta, delta_size, &delta_size);
      free(to_free);
    }
  }

  if (delta && delta_size < deflate_size) {
    char *s = xstrfmt("%"PRIuMAX , (uintmax_t)orig_size);
    emit_diff_symbol(o, DIFF_SYMBOL_BINARY_DIFF_HEADER_DELTA,
         s, strlen(s), 0);
    free(s);
    free(deflated);
    data = delta;
    data_size = delta_size;
  } else {
    char *s = xstrfmt("%"PRIuMAX, (uintmax_t)two->size);
    emit_diff_symbol(o, DIFF_SYMBOL_BINARY_DIFF_HEADER_LITERAL,
         s, strlen(s), 0);
    free(s);
    free(delta);
    data = deflated;
    data_size = deflate_size;
  }

  /* emit data encoded in base85 */
  cp = data;
  while (data_size) {
    int len;
    int bytes = (52 < data_size) ? 52 : data_size;
    char line[71];
    data_size -= bytes;
    if (bytes <= 26)
      line[0] = bytes + 'A' - 1;
    else
      line[0] = bytes - 26 + 'a' - 1;
    encode_85(line + 1, cp, bytes);
    cp = (char *) cp + bytes;

    len = strlen(line);
    line[len++] = '\n';
    line[len] = '\0';

    emit_diff_symbol(o, DIFF_SYMBOL_BINARY_DIFF_BODY,
         line, len, 0);
  }
  emit_diff_symbol(o, DIFF_SYMBOL_BINARY_DIFF_FOOTER, NULL, 0, 0);
  free(data);
}

static void emit_binary_diff(struct diff_options *o,
           mmfile_t *one, mmfile_t *two)
{
  emit_diff_symbol(o, DIFF_SYMBOL_BINARY_DIFF_HEADER, NULL, 0, 0);
  emit_binary_diff_body(o, one, two);
  emit_binary_diff_body(o, two, one);
}

int diff_filespec_is_binary(struct repository *r,
          struct diff_filespec *one)
{
  struct diff_populate_filespec_options dpf_options = {
    .check_binary = 1,
  };

  if (one->is_binary == -1) {
    diff_filespec_load_driver(one, r->index);
    if (one->driver->binary != -1)
      one->is_binary = one->driver->binary;
    else {
      if (!one->data && DIFF_FILE_VALID(one))
        diff_populate_filespec(r, one, &dpf_options);
      if (one->is_binary == -1 && one->data)
        one->is_binary = buffer_is_binary(one->data,
            one->size);
      if (one->is_binary == -1)
        one->is_binary = 0;
    }
  }
  return one->is_binary;
}

static const struct userdiff_funcname *
diff_funcname_pattern(struct diff_options *o, struct diff_filespec *one)
{
  diff_filespec_load_driver(one, o->repo->index);
  return one->driver->funcname.pattern ? &one->driver->funcname : NULL;
}

void diff_set_mnemonic_prefix(struct diff_options *options, const char *a, const char *b)
{
  if (!options->a_prefix)
    options->a_prefix = a;
  if (!options->b_prefix)
    options->b_prefix = b;
}

void diff_set_noprefix(struct diff_options *options)
{
  options->a_prefix = options->b_prefix = "";
}

void diff_set_default_prefix(struct diff_options *options)
{
  options->a_prefix = diff_src_prefix ? diff_src_prefix : "a/";
  options->b_prefix = diff_dst_prefix ? diff_dst_prefix : "b/";
}

struct userdiff_driver *get_textconv(struct repository *r,
             struct diff_filespec *one)
{
  if (!DIFF_FILE_VALID(one))
    return NULL;

  diff_filespec_load_driver(one, r->index);
  return userdiff_get_textconv(r, one->driver);
}

static struct string_list *additional_headers(struct diff_options *o,
                const char *path)
{
  if (!o->additional_path_headers)
    return NULL;
  return strmap_get(o->additional_path_headers, path);
}

static void add_formatted_header(struct strbuf *msg,
          const char *header,
          const char *line_prefix,
          const char *meta,
          const char *reset)
{
  const char *next, *newline;

  for (next = header; *next; next = newline) {
    newline = strchrnul(next, '\n');
    strbuf_addf(msg, "%s%s%.*s%s\n", line_prefix, meta,
          (int)(newline - next), next, reset);
    if (*newline)
      newline++;
  }
}

static void add_formatted_headers(struct strbuf *msg,
          struct string_list *more_headers,
          const char *line_prefix,
          const char *meta,
          const char *reset)
{
  int i;

  for (i = 0; i < more_headers->nr; i++)
    add_formatted_header(msg, more_headers->items[i].string,
             line_prefix, meta, reset);
}

static int diff_filepair_is_phoney(struct diff_filespec *one,
           struct diff_filespec *two)
{
  /*
   * This function specifically looks for pairs injected by
   * create_filepairs_for_header_only_notifications().  Such
   * pairs are "phoney" in that they do not represent any
   * content or even mode difference, but were inserted because
   * diff_queued_diff previously had no pair associated with
   * that path but we needed some pair to avoid losing the
   * "remerge CONFLICT" header associated with the path.
   */
  return !DIFF_FILE_VALID(one) && !DIFF_FILE_VALID(two);
}

static int set_diff_algorithm(struct diff_options *opts,
            const char *alg)
{
  long value = parse_algorithm_value(alg);

  if (value < 0)
    return -1;

  /* clear out previous settings */
  opts->xdl_opts &= ~XDF_DIFF_ALGORITHM_MASK;
  opts->xdl_opts |= value;

  return 0;
}

static void builtin_diff(const char *name_a,
       const char *name_b,
       struct diff_filespec *one,
       struct diff_filespec *two,
       const char *xfrm_msg,
       int must_show_header,
       struct diff_options *o,
       int complete_rewrite,
       const struct range_set *line_ranges)
{
  mmfile_t mf1, mf2;
  const char *lbl[2];
  char *a_one, *b_two;
  const char *meta = diff_get_color_opt(o, DIFF_METAINFO);
  const char *reset = diff_get_color_opt(o, DIFF_RESET);
  const char *a_prefix, *b_prefix;
  struct userdiff_driver *textconv_one = NULL;
  struct userdiff_driver *textconv_two = NULL;
  struct strbuf header = STRBUF_INIT;
  const char *line_prefix = diff_line_prefix(o);

  diff_set_mnemonic_prefix(o, "a/", "b/");
  if (o->flags.reverse_diff) {
    a_prefix = o->b_prefix;
    b_prefix = o->a_prefix;
  } else {
    a_prefix = o->a_prefix;
    b_prefix = o->b_prefix;
  }

  if (o->submodule_format == DIFF_SUBMODULE_LOG &&
      (!one->mode || S_ISGITLINK(one->mode)) &&
      (!two->mode || S_ISGITLINK(two->mode)) &&
      (!diff_filepair_is_phoney(one, two))) {
    show_submodule_diff_summary(o, one->path ? one->path : two->path,
        &one->oid, &two->oid,
        two->dirty_submodule);
    o->found_changes = 1;
    return;
  } else if (o->submodule_format == DIFF_SUBMODULE_INLINE_DIFF &&
       (!one->mode || S_ISGITLINK(one->mode)) &&
       (!two->mode || S_ISGITLINK(two->mode)) &&
       (!diff_filepair_is_phoney(one, two))) {
    show_submodule_inline_diff(o, one->path ? one->path : two->path,
        &one->oid, &two->oid,
        two->dirty_submodule);
    o->found_changes = 1;
    return;
  }

  if (o->flags.allow_textconv) {
    textconv_one = get_textconv(o->repo, one);
    textconv_two = get_textconv(o->repo, two);
  }

  /* Never use a non-valid filename anywhere if at all possible */
  name_a = DIFF_FILE_VALID(one) ? name_a : name_b;
  name_b = DIFF_FILE_VALID(two) ? name_b : name_a;

  a_one = quote_two(a_prefix, name_a + (*name_a == '/'));
  b_two = quote_two(b_prefix, name_b + (*name_b == '/'));
  lbl[0] = DIFF_FILE_VALID(one) ? a_one : "/dev/null";
  lbl[1] = DIFF_FILE_VALID(two) ? b_two : "/dev/null";
  if (diff_filepair_is_phoney(one, two)) {
    /*
     * We should only reach this point for pairs generated from
     * create_filepairs_for_header_only_notifications().  For
     * these, we want to avoid the "/dev/null" special casing
     * above, because we do not want such pairs shown as either
     * "new file" or "deleted file" below.
     */
    lbl[0] = a_one;
    lbl[1] = b_two;
  }
  strbuf_addf(&header, "%s%sdiff --git %s %s%s\n", line_prefix, meta, a_one, b_two, reset);
  if (lbl[0][0] == '/') {
    /* /dev/null */
    strbuf_addf(&header, "%s%snew file mode %06o%s\n", line_prefix, meta, two->mode, reset);
    if (xfrm_msg)
      strbuf_addstr(&header, xfrm_msg);
    o->found_changes = 1;
    must_show_header = 1;
  }
  else if (lbl[1][0] == '/') {
    strbuf_addf(&header, "%s%sdeleted file mode %06o%s\n", line_prefix, meta, one->mode, reset);
    if (xfrm_msg)
      strbuf_addstr(&header, xfrm_msg);
    o->found_changes = 1;
    must_show_header = 1;
  }
  else {
    if (one->mode != two->mode) {
      strbuf_addf(&header, "%s%sold mode %06o%s\n", line_prefix, meta, one->mode, reset);
      strbuf_addf(&header, "%s%snew mode %06o%s\n", line_prefix, meta, two->mode, reset);
      o->found_changes = 1;
      must_show_header = 1;
    }
    if (xfrm_msg)
      strbuf_addstr(&header, xfrm_msg);

    /*
     * we do not run diff between different kind
     * of objects.
     */
    if ((one->mode ^ two->mode) & S_IFMT)
      goto free_ab_and_return;
    if (complete_rewrite &&
        (textconv_one || !diff_filespec_is_binary(o->repo, one)) &&
        (textconv_two || !diff_filespec_is_binary(o->repo, two))) {
      emit_diff_symbol(o, DIFF_SYMBOL_HEADER,
           header.buf, header.len, 0);
      strbuf_reset(&header);
      emit_rewrite_diff(name_a, name_b, one, two,
            textconv_one, textconv_two, o);
      o->found_changes = 1;
      goto free_ab_and_return;
    }
  }

  if (o->irreversible_delete && lbl[1][0] == '/') {
    emit_diff_symbol(o, DIFF_SYMBOL_HEADER, header.buf,
         header.len, 0);
    strbuf_reset(&header);
    goto free_ab_and_return;
  } else if (!o->flags.text &&
       ( (!textconv_one && diff_filespec_is_binary(o->repo, one)) ||
         (!textconv_two && diff_filespec_is_binary(o->repo, two)) )) {
    struct strbuf sb = STRBUF_INIT;
    if (!one->data && !two->data &&
        S_ISREG(one->mode) && S_ISREG(two->mode) &&
        !o->flags.binary) {
      if (oideq(&one->oid, &two->oid)) {
        if (must_show_header)
          emit_diff_symbol(o, DIFF_SYMBOL_HEADER,
               header.buf, header.len,
               0);
        goto free_ab_and_return;
      }
      emit_diff_symbol(o, DIFF_SYMBOL_HEADER,
           header.buf, header.len, 0);
      strbuf_addf(&sb, "%sBinary files %s and %s differ\n",
            diff_line_prefix(o), lbl[0], lbl[1]);
      emit_diff_symbol(o, DIFF_SYMBOL_BINARY_FILES,
           sb.buf, sb.len, 0);
      strbuf_release(&sb);
      o->found_changes = 1;
      goto free_ab_and_return;
    }
    if (fill_mmfile(o->repo, &mf1, one) < 0 ||
        fill_mmfile(o->repo, &mf2, two) < 0)
      die("unable to read files to diff");
    /* Quite common confusing case */
    if (mf1.size == mf2.size &&
        !memcmp(mf1.ptr, mf2.ptr, mf1.size)) {
      if (must_show_header)
        emit_diff_symbol(o, DIFF_SYMBOL_HEADER,
             header.buf, header.len, 0);
      goto free_ab_and_return;
    }
    emit_diff_symbol(o, DIFF_SYMBOL_HEADER, header.buf, header.len, 0);
    strbuf_reset(&header);
    if (o->flags.binary)
      emit_binary_diff(o, &mf1, &mf2);
    else {
      strbuf_addf(&sb, "%sBinary files %s and %s differ\n",
            diff_line_prefix(o), lbl[0], lbl[1]);
      emit_diff_symbol(o, DIFF_SYMBOL_BINARY_FILES,
           sb.buf, sb.len, 0);
      strbuf_release(&sb);
    }
    o->found_changes = 1;
  } else {
    /* Crazy xdl interfaces.. */
    const char *diffopts;
    const char *v;
    xpparam_t xpp;
    xdemitconf_t xecfg;
    struct emit_callback ecbdata;
    unsigned ws_rule;
    const struct userdiff_funcname *pe;

    if (must_show_header) {
      emit_diff_symbol(o, DIFF_SYMBOL_HEADER,
           header.buf, header.len, 0);
      strbuf_reset(&header);
    }

    mf1.size = fill_textconv(o->repo, textconv_one, one, &mf1.ptr);
    mf2.size = fill_textconv(o->repo, textconv_two, two, &mf2.ptr);

    ws_rule = whitespace_rule(o->repo->index, name_b);

    /* symlink being an incomplete line is not a news */
    if (DIFF_FILE_VALID(two) && S_ISLNK(two->mode))
      ws_rule &= ~WS_INCOMPLETE_LINE;

    pe = diff_funcname_pattern(o, one);
    if (!pe)
      pe = diff_funcname_pattern(o, two);

    memset(&xpp, 0, sizeof(xpp));
    memset(&xecfg, 0, sizeof(xecfg));
    memset(&ecbdata, 0, sizeof(ecbdata));
    if (o->flags.suppress_diff_headers)
      lbl[0] = NULL;
    ecbdata.label_path = lbl;
    ecbdata.color_diff = o->use_color;
    ecbdata.ws_rule = ws_rule;
    if (ecbdata.ws_rule & WS_BLANK_AT_EOF)
      check_blank_at_eof(&mf1, &mf2, &ecbdata);
    ecbdata.opt = o;
    if (header.len && !o->flags.suppress_diff_headers)
      ecbdata.header = &header;
    xpp.flags = o->xdl_opts;
    xpp.ignore_regex = o->ignore_regex;
    xpp.ignore_regex_nr = o->ignore_regex_nr;
    xpp.anchors = o->anchors;
    xpp.anchors_nr = o->anchors_nr;
    xecfg.ctxlen = o->context;
    xecfg.interhunkctxlen = o->interhunkcontext;
    xecfg.flags = XDL_EMIT_FUNCNAMES;
    if (o->flags.funccontext)
      xecfg.flags |= XDL_EMIT_FUNCCONTEXT;
    if (pe)
      xdiff_set_find_func(&xecfg, pe->pattern, pe->cflags);

    diffopts = getenv("GIT_DIFF_OPTS");
    if (!diffopts)
      ;
    else if (skip_prefix(diffopts, "--unified=", &v))
      xecfg.ctxlen = strtoul(v, NULL, 10);
    else if (skip_prefix(diffopts, "-u", &v))
      xecfg.ctxlen = strtoul(v, NULL, 10);

    if (o->word_diff)
      init_diff_words_data(&ecbdata, o, one, two);
    if (!o->file) {
      /*
       * Unlike the normal output case, we need to ignore the
       * return value from xdi_diff_outf() here, because
       * xdi_diff_outf() takes non-zero return from its
       * callback function as a sign of error and returns
       * early (which is why we return non-zero from our
       * callback, quick_consume()).  Unfortunately,
       * xdi_diff_outf() signals an error by returning
       * non-zero.
       */
      xdi_diff_outf(&mf1, &mf2, NULL, quick_consume,
              &ecbdata, &xpp, &xecfg);
    } else if (line_ranges) {
      struct line_range_callback lr_state;
      unsigned int i;
      long max_span = 0;

      memset(&lr_state, 0, sizeof(lr_state));
      lr_state.orig_line_fn = fn_out_consume;
      lr_state.orig_cb_data = &ecbdata;
      lr_state.ranges = line_ranges;
      strbuf_init(&lr_state.rhunk, 0);
      strbuf_init(&lr_state.pending_rm, 0);

      /*
       * Inflate ctxlen so that all changes within
       * any single range are merged into one xdiff
       * hunk and the inter-change context is emitted.
       * The callback clips back to range boundaries.
       *
       * The optimal ctxlen depends on where changes
       * fall within the range, which is only known
       * after xdiff runs; the max range span is the
       * upper bound that guarantees correctness in a
       * single pass.
       */
      for (i = 0; i < line_ranges->nr; i++) {
        long span = line_ranges->ranges[i].end -
              line_ranges->ranges[i].start;
        if (span > max_span)
          max_span = span;
      }
      if (max_span > xecfg.ctxlen)
        xecfg.ctxlen = max_span;

      if (xdi_diff_outf(&mf1, &mf2,
            line_range_hunk_fn,
            line_range_line_fn,
            &lr_state, &xpp, &xecfg))
        die("unable to generate diff for %s",
            one->path);

      flush_rhunk(&lr_state);
      if (lr_state.ret)
        die("unable to generate diff for %s",
            one->path);
      strbuf_release(&lr_state.rhunk);
      strbuf_release(&lr_state.pending_rm);
    } else if (xdi_diff_outf(&mf1, &mf2, NULL, fn_out_consume,
           &ecbdata, &xpp, &xecfg))
      die("unable to generate diff for %s", one->path);
    if (o->word_diff)
      free_diff_words_data(&ecbdata);
    if (textconv_one)
      free(mf1.ptr);
    if (textconv_two)
      free(mf2.ptr);
    xdiff_clear_find_func(&xecfg);
  }

 free_ab_and_return:
  strbuf_release(&header);
  diff_free_filespec_data(one);
  diff_free_filespec_data(two);
  free(a_one);
  free(b_two);
  return;
}

static const char *get_compact_summary(const struct diff_filepair *p, int is_renamed)
{
  if (!is_renamed) {
    if (p->status == DIFF_STATUS_ADDED) {
      if (S_ISLNK(p->two->mode))
        return "new +l";
      else if ((p->two->mode & 0777) == 0755)
        return "new +x";
      else
        return "new";
    } else if (p->status == DIFF_STATUS_DELETED)
      return "gone";
  }
  if (S_ISLNK(p->one->mode) && !S_ISLNK(p->two->mode))
    return "mode -l";
  else if (!S_ISLNK(p->one->mode) && S_ISLNK(p->two->mode))
    return "mode +l";
  else if ((p->one->mode & 0777) == 0644 &&
     (p->two->mode & 0777) == 0755)
    return "mode +x";
  else if ((p->one->mode & 0777) == 0755 &&
     (p->two->mode & 0777) == 0644)
    return "mode -x";
  return NULL;
}

static void builtin_diffstat(const char *name_a, const char *name_b,
           struct diff_filespec *one,
           struct diff_filespec *two,
           struct diffstat_t *diffstat,
           struct diff_options *o,
           struct diff_filepair *p)
{
  mmfile_t mf1, mf2;
  struct diffstat_file *data;
  int may_differ;
  int complete_rewrite = 0;

  if (!DIFF_PAIR_UNMERGED(p)) {
    if (p->status == DIFF_STATUS_MODIFIED && p->score)
      complete_rewrite = 1;
  }

  data = diffstat_add(diffstat, name_a, name_b);
  data->is_interesting = p->status != DIFF_STATUS_UNKNOWN;
  if (o->flags.stat_with_summary)
    data->comments = get_compact_summary(p, data->is_renamed);

  if (!one || !two) {
    data->is_unmerged = 1;
    return;
  }

  /* saves some reads if true, not a guarantee of diff outcome */
  may_differ = !(one->oid_valid && two->oid_valid &&
      oideq(&one->oid, &two->oid));

  if (diff_filespec_is_binary(o->repo, one) ||
      diff_filespec_is_binary(o->repo, two)) {
    data->is_binary = 1;
    if (!may_differ) {
      data->added = 0;
      data->deleted = 0;
    } else {
      data->added = diff_filespec_size(o->repo, two);
      data->deleted = diff_filespec_size(o->repo, one);
    }
  }

  else if (complete_rewrite) {
    diff_populate_filespec(o->repo, one, NULL);
    diff_populate_filespec(o->repo, two, NULL);
    data->deleted = count_lines(one->data, one->size);
    data->added = count_lines(two->data, two->size);
  }

  else if (may_differ) {
    /* Crazy xdl interfaces.. */
    xpparam_t xpp;
    xdemitconf_t xecfg;

    if (fill_mmfile(o->repo, &mf1, one) < 0 ||
        fill_mmfile(o->repo, &mf2, two) < 0)
      die("unable to read files to diff");

    memset(&xpp, 0, sizeof(xpp));
    memset(&xecfg, 0, sizeof(xecfg));
    xpp.flags = o->xdl_opts;
    xpp.ignore_regex = o->ignore_regex;
    xpp.ignore_regex_nr = o->ignore_regex_nr;
    xpp.anchors = o->anchors;
    xpp.anchors_nr = o->anchors_nr;
    xecfg.ctxlen = o->context;
    xecfg.interhunkctxlen = o->interhunkcontext;
    xecfg.flags = XDL_EMIT_NO_HUNK_HDR;
    if (xdi_diff_outf(&mf1, &mf2, NULL,
          diffstat_consume, diffstat, &xpp, &xecfg))
      die("unable to generate diffstat for %s", one->path);

    if (DIFF_FILE_VALID(one) && DIFF_FILE_VALID(two)) {
      struct diffstat_file *file =
        diffstat->files[diffstat->nr - 1];
      /*
       * Omit diffstats of modified files where nothing changed.
       * Even if may_differ, this might be the case due to
       * ignoring whitespace changes, etc.
       *
       * But note that we special-case additions, deletions,
       * renames, and mode changes as adding an empty file,
       * for example is still of interest.
       */
      if ((p->status == DIFF_STATUS_MODIFIED)
        && !file->added
        && !file->deleted
        && one->mode == two->mode) {
        free_diffstat_file(file);
        diffstat->nr--;
      }
    }
  }

  diff_free_filespec_data(one);
  diff_free_filespec_data(two);
}

static void builtin_checkdiff(const char *name_a, const char *name_b,
            const char *attr_path,
            struct diff_filespec *one,
            struct diff_filespec *two,
            struct diff_options *o)
{
  mmfile_t mf1, mf2;
  struct checkdiff_t data;

  if (!two)
    return;

  memset(&data, 0, sizeof(data));
  data.filename = name_b ? name_b : name_a;
  data.lineno = 0;
  data.o = o;
  data.ws_rule = whitespace_rule(o->repo->index, attr_path);
  data.conflict_marker_size = ll_merge_marker_size(o->repo->index, attr_path);

  /* symlink being an incomplete line is not a news */
  if (DIFF_FILE_VALID(two) && S_ISLNK(two->mode))
    data.ws_rule &= ~WS_INCOMPLETE_LINE;

  if (fill_mmfile(o->repo, &mf1, one) < 0 ||
      fill_mmfile(o->repo, &mf2, two) < 0)
    die("unable to read files to diff");

  /*
   * All the other codepaths check both sides, but not checking
   * the "old" side here is deliberate.  We are checking the newly
   * introduced changes, and as long as the "new" side is text, we
   * can and should check what it introduces.
   */
  if (diff_filespec_is_binary(o->repo, two))
    goto free_and_return;
  else {
    /* Crazy xdl interfaces.. */
    xpparam_t xpp;
    xdemitconf_t xecfg;

    memset(&xpp, 0, sizeof(xpp));
    memset(&xecfg, 0, sizeof(xecfg));
    xecfg.ctxlen = 1; /* at least one context line */
    xpp.flags = 0;
    if (xdi_diff_outf(&mf1, &mf2, checkdiff_consume_hunk,
          checkdiff_consume, &data,
          &xpp, &xecfg))
      die("unable to generate checkdiff for %s", one->path);

    if (data.ws_rule & WS_BLANK_AT_EOF) {
      struct emit_callback ecbdata;
      int blank_at_eof;

      ecbdata.ws_rule = data.ws_rule;
      check_blank_at_eof(&mf1, &mf2, &ecbdata);
      blank_at_eof = ecbdata.blank_at_eof_in_postimage;

      if (blank_at_eof) {
        static char *err;
        if (!err)
          err = whitespace_error_string(WS_BLANK_AT_EOF);
        fprintf(o->file, "%s:%d: %s.\n",
          data.filename, blank_at_eof, err);
        data.status = 1; /* report errors */
      }
    }
  }
 free_and_return:
  diff_free_filespec_data(one);
  diff_free_filespec_data(two);
  if (data.status)
    o->flags.check_failed = 1;
}

struct diff_filespec *alloc_filespec(const char *path)
{
  struct diff_filespec *spec;

  FLEXPTR_ALLOC_STR(spec, path, path);
  spec->count = 1;
  spec->is_binary = -1;
  return spec;
}

void free_filespec(struct diff_filespec *spec)
{
  if (!--spec->count) {
    diff_free_filespec_data(spec);
    free(spec);
  }
}

void fill_filespec(struct diff_filespec *spec, const struct object_id *oid,
       int oid_valid, unsigned short mode)
{
  if (mode) {
    spec->mode = canon_mode(mode);
    oidcpy(&spec->oid, oid);
    spec->oid_valid = oid_valid;
  }
}

/*
 * Given a name and sha1 pair, if the index tells us the file in
 * the work tree has that object contents, return true, so that
 * prepare_temp_file() does not have to inflate and extract.
 */
static int reuse_worktree_file(struct index_state *istate,
             const char *name,
             const struct object_id *oid,
             int want_file)
{
  const struct cache_entry *ce;
  struct stat st;
  int pos, len;

  /*
   * We do not read the cache ourselves here, because the
   * benchmark with my previous version that always reads cache
   * shows that it makes things worse for diff-tree comparing
   * two linux-2.6 kernel trees in an already checked out work
   * tree.  This is because most diff-tree comparisons deal with
   * only a small number of files, while reading the cache is
   * expensive for a large project, and its cost outweighs the
   * savings we get by not inflating the object to a temporary
   * file.  Practically, this code only helps when we are used
   * by diff-cache --cached, which does read the cache before
   * calling us.
   */
  if (!istate->cache)
    return 0;

  /* We want to avoid the working directory if our caller
   * doesn't need the data in a normal file, this system
   * is rather slow with its stat/open/mmap/close syscalls,
   * and the object is contained in a pack file.  The pack
   * is probably already open and will be faster to obtain
   * the data through than the working directory.  Loose
   * objects however would tend to be slower as they need
   * to be individually opened and inflated.
   */
  if (!FAST_WORKING_DIRECTORY && !want_file &&
      has_object_pack(istate->repo, oid))
    return 0;

  /*
   * Similarly, if we'd have to convert the file contents anyway, that
   * makes the optimization not worthwhile.
   */
  if (!want_file && would_convert_to_git(istate, name))
    return 0;

  /*
   * If this path does not match our sparse-checkout definition,
   * then the file will not be in the working directory.
   */
  if (!path_in_sparse_checkout(name, istate))
    return 0;

  len = strlen(name);
  pos = index_name_pos(istate, name, len);
  if (pos < 0)
    return 0;
  ce = istate->cache[pos];

  /*
   * This is not the sha1 we are looking for, or
   * unreusable because it is not a regular file.
   */
  if (!oideq(oid, &ce->oid) || !S_ISREG(ce->ce_mode))
    return 0;

  /*
   * If ce is marked as "assume unchanged", there is no
   * guarantee that work tree matches what we are looking for.
   */
  if ((ce->ce_flags & CE_VALID) || ce_skip_worktree(ce))
    return 0;

  /*
   * If ce matches the file in the work tree, we can reuse it.
   */
  if (ce_uptodate(ce) ||
      (!lstat(name, &st) && !ie_match_stat(istate, ce, &st, 0)))
    return 1;

  return 0;
}

static int diff_populate_gitlink(struct diff_filespec *s, int size_only)
{
  struct strbuf buf = STRBUF_INIT;
  const char *dirty = "";

  /* Are we looking at the work tree? */
  if (s->dirty_submodule)
    dirty = "-dirty";

  strbuf_addf(&buf, "Subproject commit %s%s\n",
        oid_to_hex(&s->oid), dirty);
  s->size = buf.len;
  if (size_only) {
    s->data = NULL;
    strbuf_release(&buf);
  } else {
    s->data = strbuf_detach(&buf, NULL);
    s->should_free = 1;
  }
  return 0;
}

/*
 * While doing rename detection and pickaxe operation, we may need to
 * grab the data for the blob (or file) for our own in-core comparison.
 * diff_filespec has data and size fields for this purpose.
 */
int diff_populate_filespec(struct repository *r,
         struct diff_filespec *s,
         const struct diff_populate_filespec_options *options)
{
  int size_only = options ? options->check_size_only : 0;
  int check_binary = options ? options->check_binary : 0;
  int err = 0;
  int conv_flags = global_conv_flags_eol;
  /*
   * demote FAIL to WARN to allow inspecting the situation
   * instead of refusing.
   */
  if (conv_flags & CONV_EOL_RNDTRP_DIE)
    conv_flags = CONV_EOL_RNDTRP_WARN;

  if (!DIFF_FILE_VALID(s))
    die("internal error: asking to populate invalid file.");
  if (S_ISDIR(s->mode))
    return -1;

  if (s->data)
    return 0;

  if (size_only && 0 < s->size)
    return 0;

  if (S_ISGITLINK(s->mode))
    return diff_populate_gitlink(s, size_only);

  if (!s->oid_valid ||
      reuse_worktree_file(r->index, s->path, &s->oid, 0)) {
    struct strbuf buf = STRBUF_INIT;
    struct stat st;
    int fd;

    if (lstat(s->path, &st) < 0) {
    err_empty:
      err = -1;
    empty:
      s->data = (char *)"";
      s->size = 0;
      return err;
    }
    s->size = xsize_t(st.st_size);
    if (!s->size)
      goto empty;
    if (S_ISLNK(st.st_mode)) {
      struct strbuf sb = STRBUF_INIT;

      if (strbuf_readlink(&sb, s->path, s->size))
        goto err_empty;
      s->size = sb.len;
      s->data = strbuf_detach(&sb, NULL);
      s->should_free = 1;
      return 0;
    }

    /*
     * Even if the caller would be happy with getting
     * only the size, we cannot return early at this
     * point if the path requires us to run the content
     * conversion.
     */
    if (size_only && !would_convert_to_git(r->index, s->path))
      return 0;

    /*
     * Note: this check uses xsize_t(st.st_size) that may
     * not be the true size of the blob after it goes
     * through convert_to_git().  This may not strictly be
     * correct, but the whole point of big_file_threshold
     * and is_binary check being that we want to avoid
     * opening the file and inspecting the contents, this
     * is probably fine.
     */
    if (check_binary &&
        s->size > repo_settings_get_big_file_threshold(the_repository) &&
        s->is_binary == -1) {
      s->is_binary = 1;
      return 0;
    }
    fd = open(s->path, O_RDONLY);
    if (fd < 0)
      goto err_empty;
    s->data = xmmap(NULL, s->size, PROT_READ, MAP_PRIVATE, fd, 0);
    close(fd);
    s->should_munmap = 1;

    /*
     * Convert from working tree format to canonical git format
     */
    if (convert_to_git(r->index, s->path, s->data, s->size, &buf, conv_flags)) {
      size_t size = 0;
      munmap(s->data, s->size);
      s->should_munmap = 0;
      s->data = strbuf_detach(&buf, &size);
      s->size = size;
      s->should_free = 1;
    }
  }
  else {
    size_t size_st = 0;
    struct object_info info = {
      .sizep = &size_st
    };

    if (!(size_only || check_binary))
      /*
       * Set contentp, since there is no chance that merely
       * the size is sufficient.
       */
      info.contentp = &s->data;

    if (options && options->missing_object_cb) {
      if (!odb_read_object_info_extended(r->objects, &s->oid, &info,
                 OBJECT_INFO_LOOKUP_REPLACE |
                 OBJECT_INFO_SKIP_FETCH_OBJECT))
        goto object_read;
      options->missing_object_cb(options->missing_object_data);
    }
    if (odb_read_object_info_extended(r->objects, &s->oid, &info,
              OBJECT_INFO_LOOKUP_REPLACE))
      die("unable to read %s", oid_to_hex(&s->oid));

object_read:
    s->size = cast_size_t_to_ulong(size_st);
    if (size_only || check_binary) {
      if (size_only)
        return 0;
      if (s->size > repo_settings_get_big_file_threshold(the_repository) &&
          s->is_binary == -1) {
        s->is_binary = 1;
        return 0;
      }
    }
    if (!info.contentp) {
      info.contentp = &s->data;
      if (odb_read_object_info_extended(r->objects, &s->oid, &info,
                OBJECT_INFO_LOOKUP_REPLACE))
        die("unable to read %s", oid_to_hex(&s->oid));
      s->size = cast_size_t_to_ulong(size_st);
    }
    s->should_free = 1;
  }
  return 0;
}

void diff_free_filespec_blob(struct diff_filespec *s)
{
  if (s->should_free)
    free(s->data);
  else if (s->should_munmap)
    munmap(s->data, s->size);

  if (s->should_free || s->should_munmap) {
    s->should_free = s->should_munmap = 0;
    s->data = NULL;
  }
}

void diff_free_filespec_data(struct diff_filespec *s)
{
  if (!s)
    return;

  diff_free_filespec_blob(s);
  FREE_AND_NULL(s->cnt_data);
}

static void prep_temp_blob(struct index_state *istate,
         const char *path, struct diff_tempfile *temp,
         void *blob,
         unsigned long size,
         const struct object_id *oid,
         int mode)
{
  struct strbuf buf = STRBUF_INIT;
  char *path_dup = xstrdup(path);
  const char *base = basename(path_dup);
  struct checkout_metadata meta;

  init_checkout_metadata(&meta, NULL, NULL, oid);

  temp->tempfile = mks_tempfile_dt("git-blob-XXXXXX", base);
  if (!temp->tempfile)
    die_errno("unable to create temp-file");
  if (convert_to_working_tree(istate, path,
      (const char *)blob, (size_t)size, &buf, &meta)) {
    blob = buf.buf;
    size = buf.len;
  }
  if (write_in_full(temp->tempfile->fd, blob, size) < 0 ||
      close_tempfile_gently(temp->tempfile))
    die_errno("unable to write temp-file");
  temp->name = get_tempfile_path(temp->tempfile);
  oid_to_hex_r(temp->hex, oid);
  xsnprintf(temp->mode, sizeof(temp->mode), "%06o", mode);
  strbuf_release(&buf);
  free(path_dup);
}

static struct diff_tempfile *prepare_temp_file(struct repository *r,
                 struct diff_filespec *one)
{
  struct diff_tempfile *temp = claim_diff_tempfile();

  if (!DIFF_FILE_VALID(one)) {
  not_a_valid_file:
    /* A '-' entry produces this for file-2, and
     * a '+' entry produces this for file-1.
     */
    temp->name = "/dev/null";
    xsnprintf(temp->hex, sizeof(temp->hex), ".");
    xsnprintf(temp->mode, sizeof(temp->mode), ".");
    return temp;
  }

  if (!S_ISGITLINK(one->mode) &&
      (!one->oid_valid ||
       reuse_worktree_file(r->index, one->path, &one->oid, 1))) {
    struct stat st;
    if (lstat(one->path, &st) < 0) {
      if (errno == ENOENT)
        goto not_a_valid_file;
      die_errno("stat(%s)", one->path);
    }
    if (S_ISLNK(st.st_mode)) {
      struct strbuf sb = STRBUF_INIT;
      if (strbuf_readlink(&sb, one->path, st.st_size) < 0)
        die_errno("readlink(%s)", one->path);
      prep_temp_blob(r->index, one->path, temp, sb.buf, sb.len,
               (one->oid_valid ?
          &one->oid : null_oid(the_hash_algo)),
               (one->oid_valid ?
          one->mode : S_IFLNK));
      strbuf_release(&sb);
    }
    else {
      /* we can borrow from the file in the work tree */
      temp->name = one->path;
      if (!one->oid_valid)
        oid_to_hex_r(temp->hex, null_oid(the_hash_algo));
      else
        oid_to_hex_r(temp->hex, &one->oid);
      /* Even though we may sometimes borrow the
       * contents from the work tree, we always want
       * one->mode.  mode is trustworthy even when
       * !(one->oid_valid), as long as
       * DIFF_FILE_VALID(one).
       */
      xsnprintf(temp->mode, sizeof(temp->mode), "%06o", one->mode);
    }
    return temp;
  }
  else {
    if (diff_populate_filespec(r, one, NULL))
      die("cannot read data blob for %s", one->path);
    prep_temp_blob(r->index, one->path, temp,
             one->data, one->size,
             &one->oid, one->mode);
  }
  return temp;
}

static void add_external_diff_name(struct repository *r,
           struct strvec *argv,
           struct diff_filespec *df)
{
  struct diff_tempfile *temp = prepare_temp_file(r, df);
  strvec_push(argv, temp->name);
  strvec_push(argv, temp->hex);
  strvec_push(argv, temp->mode);
}

/* An external diff command takes:
 *
 * diff-cmd name infile1 infile1-sha1 infile1-mode \
 *               infile2 infile2-sha1 infile2-mode [ rename-to ]
 *
 */
static void run_external_diff(const struct external_diff *pgm,
            const char *name,
            const char *other,
            struct diff_filespec *one,
            struct diff_filespec *two,
            const char *xfrm_msg,
            struct diff_options *o)
{
  struct child_process cmd = CHILD_PROCESS_INIT;
  struct diff_queue_struct *q = &diff_queued_diff;
  int rc;

  /*
   * Trivial equality is handled by diff_unmodified_pair() before
   * we get here.  If we don't need to show the diff and the
   * external diff program lacks the ability to tell us whether
   * it's empty then we consider it non-empty without even asking.
   */
  if (!pgm->trust_exit_code && !o->file) {
    o->found_changes = 1;
    return;
  }

  strvec_push(&cmd.args, pgm->cmd);
  strvec_push(&cmd.args, name);

  if (one && two) {
    add_external_diff_name(o->repo, &cmd.args, one);
    add_external_diff_name(o->repo, &cmd.args, two);
    if (other) {
      strvec_push(&cmd.args, other);
      if (xfrm_msg)
        strvec_push(&cmd.args, xfrm_msg);
    }
  }

  strvec_pushf(&cmd.env, "GIT_DIFF_PATH_COUNTER=%d",
         ++o->diff_path_counter);
  strvec_pushf(&cmd.env, "GIT_DIFF_PATH_TOTAL=%d", q->nr);

  diff_free_filespec_data(one);
  diff_free_filespec_data(two);
  cmd.use_shell = 1;
  if (!o->file)
    cmd.no_stdout = 1;
  else if (o->file != stdout)
    cmd.out = xdup(fileno(o->file));
  rc = run_command(&cmd);
  if (!pgm->trust_exit_code && rc == 0)
    o->found_changes = 1;
  else if (pgm->trust_exit_code && rc == 0)
    ; /* nothing */
  else if (pgm->trust_exit_code && rc == 1)
    o->found_changes = 1;
  else
    die(_("external diff died, stopping at %s"), name);

  remove_tempfile();
}

static int similarity_index(struct diff_filepair *p)
{
  return p->score * 100 / MAX_SCORE;
}

static const char *diff_abbrev_oid(const struct object_id *oid, int abbrev)
{
  if (startup_info->have_repository)
    return repo_find_unique_abbrev(the_repository, oid, abbrev);
  else {
    char *hex = oid_to_hex(oid);
    if (abbrev < 0)
      abbrev = FALLBACK_DEFAULT_ABBREV;
    if (abbrev > the_hash_algo->hexsz)
      BUG("oid abbreviation out of range: %d", abbrev);
    if (abbrev)
      hex[abbrev] = '\0';
    return hex;
  }
}

static void fill_metainfo(struct strbuf *msg,
        const char *name,
        const char *other,
        struct diff_filespec *one,
        struct diff_filespec *two,
        struct diff_options *o,
        struct diff_filepair *p,
        int *must_show_header,
        enum git_colorbool use_color)
{
  const char *set = diff_get_color(use_color, DIFF_METAINFO);
  const char *reset = diff_get_color(use_color, DIFF_RESET);
  const char *line_prefix = diff_line_prefix(o);
  struct string_list *more_headers = NULL;

  *must_show_header = 1;
  strbuf_init(msg, PATH_MAX * 2 + 300);
  switch (p->status) {
  case DIFF_STATUS_COPIED:
    strbuf_addf(msg, "%s%ssimilarity index %d%%",
          line_prefix, set, similarity_index(p));
    strbuf_addf(msg, "%s\n%s%scopy from ",
          reset,  line_prefix, set);
    quote_c_style(name, msg, NULL, 0);
    strbuf_addf(msg, "%s\n%s%scopy to ", reset, line_prefix, set);
    quote_c_style(other, msg, NULL, 0);
    strbuf_addf(msg, "%s\n", reset);
    break;
  case DIFF_STATUS_RENAMED:
    strbuf_addf(msg, "%s%ssimilarity index %d%%",
          line_prefix, set, similarity_index(p));
    strbuf_addf(msg, "%s\n%s%srename from ",
          reset, line_prefix, set);
    quote_c_style(name, msg, NULL, 0);
    strbuf_addf(msg, "%s\n%s%srename to ",
          reset, line_prefix, set);
    quote_c_style(other, msg, NULL, 0);
    strbuf_addf(msg, "%s\n", reset);
    break;
  case DIFF_STATUS_MODIFIED:
    if (p->score) {
      strbuf_addf(msg, "%s%sdissimilarity index %d%%%s\n",
            line_prefix,
            set, similarity_index(p), reset);
      break;
    }
    /* fallthru */
  default:
    *must_show_header = 0;
  }
  if ((more_headers = additional_headers(o, name))) {
    add_formatted_headers(msg, more_headers,
              line_prefix, set, reset);
    *must_show_header = 1;
  }
  if (one && two && !oideq(&one->oid, &two->oid)) {
    const unsigned hexsz = the_hash_algo->hexsz;
    int abbrev = o->abbrev ? o->abbrev : DEFAULT_ABBREV;

    if (o->flags.full_index)
      abbrev = hexsz;

    if (o->flags.binary) {
      mmfile_t mf;
      if ((!fill_mmfile(o->repo, &mf, one) &&
           diff_filespec_is_binary(o->repo, one)) ||
          (!fill_mmfile(o->repo, &mf, two) &&
           diff_filespec_is_binary(o->repo, two)))
        abbrev = hexsz;
    }
    strbuf_addf(msg, "%s%sindex %s..%s", line_prefix, set,
          diff_abbrev_oid(&one->oid, abbrev),
          diff_abbrev_oid(&two->oid, abbrev));
    if (one->mode == two->mode)
      strbuf_addf(msg, " %06o", one->mode);
    strbuf_addf(msg, "%s\n", reset);
  }
}

static void run_diff_cmd(const struct external_diff *pgm,
       const char *name,
       const char *other,
       const char *attr_path,
       struct diff_filespec *one,
       struct diff_filespec *two,
       struct strbuf *msg,
       struct diff_options *o,
       struct diff_filepair *p)
{
  const char *xfrm_msg = NULL;
  int complete_rewrite = (p->status == DIFF_STATUS_MODIFIED) && p->score;
  int must_show_header = 0;
  struct userdiff_driver *drv = NULL;

  if (o->flags.allow_external || !o->ignore_driver_algorithm)
    drv = userdiff_find_by_path(o->repo->index, attr_path);

  if (o->flags.allow_external && drv && drv->external.cmd)
    pgm = &drv->external;

  if (msg) {
    /*
     * don't use colors when the header is intended for an
     * external diff driver
     */
    fill_metainfo(msg, name, other, one, two, o, p,
            &must_show_header,
            pgm ? GIT_COLOR_NEVER : o->use_color);
    xfrm_msg = msg->len ? msg->buf : NULL;
  }

  if (pgm) {
    run_external_diff(pgm, name, other, one, two, xfrm_msg, o);
    return;
  }
  if (one && two) {
    if (!o->ignore_driver_algorithm && drv && drv->algorithm)
      set_diff_algorithm(o, drv->algorithm);

    builtin_diff(name, other ? other : name,
           one, two, xfrm_msg, must_show_header,
           o, complete_rewrite, p->line_ranges);
    if (p->status == DIFF_STATUS_COPIED ||
        p->status == DIFF_STATUS_RENAMED)
      o->found_changes = 1;
  } else {
    if (o->file)
      fprintf(o->file, "* Unmerged path %s\n", name);
    o->found_changes = 1;
  }
}

static void diff_fill_oid_info(struct diff_filespec *one, struct index_state *istate)
{
  if (DIFF_FILE_VALID(one)) {
    if (!one->oid_valid) {
      struct stat st;
      if (one->is_stdin) {
        oidclr(&one->oid, the_repository->hash_algo);
        return;
      }
      if (lstat(one->path, &st) < 0)
        die_errno("stat '%s'", one->path);
      if (index_path(istate, &one->oid, one->path, &st, 0))
        die("cannot hash %s", one->path);
    }
  }
  else
    oidclr(&one->oid, the_repository->hash_algo);
}

static void strip_prefix(int prefix_length, const char **namep, const char **otherp)
{
  /* Strip the prefix but do not molest /dev/null and absolute paths */
  if (*namep && !is_absolute_path(*namep)) {
    *namep += prefix_length;
    if (**namep == '/')
      ++*namep;
  }
  if (*otherp && !is_absolute_path(*otherp)) {
    *otherp += prefix_length;
    if (**otherp == '/')
      ++*otherp;
  }
}

static void run_diff(struct diff_filepair *p, struct diff_options *o)
{
  const struct external_diff *pgm = external_diff();
  struct strbuf msg;
  struct diff_filespec *one = p->one;
  struct diff_filespec *two = p->two;
  const char *name;
  const char *other;
  const char *attr_path;

  name  = one->path;
  other = (strcmp(name, two->path) ? two->path : NULL);
  attr_path = name;
  if (o->prefix_length)
    strip_prefix(o->prefix_length, &name, &other);

  if (!o->flags.allow_external)
    pgm = NULL;

  if (DIFF_PAIR_UNMERGED(p)) {
    run_diff_cmd(pgm, name, NULL, attr_path,
           NULL, NULL, NULL, o, p);
    return;
  }

  diff_fill_oid_info(one, o->repo->index);
  diff_fill_oid_info(two, o->repo->index);

  if (!pgm &&
      DIFF_FILE_VALID(one) && DIFF_FILE_VALID(two) &&
      (S_IFMT & one->mode) != (S_IFMT & two->mode)) {
    /*
     * a filepair that changes between file and symlink
     * needs to be split into deletion and creation.
     */
    struct diff_filespec *null = alloc_filespec(two->path);
    run_diff_cmd(NULL, name, other, attr_path,
           one, null, &msg,
           o, p);
    free(null);
    strbuf_release(&msg);

    null = alloc_filespec(one->path);
    run_diff_cmd(NULL, name, other, attr_path,
           null, two, &msg, o, p);
    free(null);
  }
  else
    run_diff_cmd(pgm, name, other, attr_path,
           one, two, &msg, o, p);

  strbuf_release(&msg);
}

static void run_diffstat(struct diff_filepair *p, struct diff_options *o,
       struct diffstat_t *diffstat)
{
  const char *name;
  const char *other;

  if (!o->ignore_driver_algorithm) {
    struct userdiff_driver *drv = userdiff_find_by_path(o->repo->index,
                    p->one->path);

    if (drv && drv->algorithm)
      set_diff_algorithm(o, drv->algorithm);
  }

  if (DIFF_PAIR_UNMERGED(p)) {
    /* unmerged */
    builtin_diffstat(p->one->path, NULL, NULL, NULL,
         diffstat, o, p);
    return;
  }

  name = p->one->path;
  other = (strcmp(name, p->two->path) ? p->two->path : NULL);

  if (o->prefix_length)
    strip_prefix(o->prefix_length, &name, &other);

  diff_fill_oid_info(p->one, o->repo->index);
  diff_fill_oid_info(p->two, o->repo->index);

  builtin_diffstat(name, other, p->one, p->two,
       diffstat, o, p);
}

static void run_checkdiff(struct diff_filepair *p, struct diff_options *o)
{
  const char *name;
  const char *other;
  const char *attr_path;

  if (DIFF_PAIR_UNMERGED(p)) {
    /* unmerged */
    return;
  }

  name = p->one->path;
  other = (strcmp(name, p->two->path) ? p->two->path : NULL);
  attr_path = other ? other : name;

  if (o->prefix_length)
    strip_prefix(o->prefix_length, &name, &other);

  diff_fill_oid_info(p->one, o->repo->index);
  diff_fill_oid_info(p->two, o->repo->index);

  builtin_checkdiff(name, other, attr_path, p->one, p->two, o);
}

void repo_diff_setup(struct repository *r, struct diff_options *options)
{
  memcpy(options, &default_diff_options, sizeof(*options));

  options->file = stdout;
  options->repo = r;

  options->output_indicators[OUTPUT_INDICATOR_NEW] = '+';
  options->output_indicators[OUTPUT_INDICATOR_OLD] = '-';
  options->output_indicators[OUTPUT_INDICATOR_CONTEXT] = ' ';
  options->abbrev = DEFAULT_ABBREV;
  options->line_termination = '\n';
  options->break_opt = -1;
  options->rename_limit = -1;
  options->dirstat_permille = diff_dirstat_permille_default;
  options->context = diff_context_default;
  options->interhunkcontext = diff_interhunk_context_default;
  options->ws_error_highlight = ws_error_highlight_default;
  options->flags.rename_empty = 1;
  options->flags.relative_name = diff_relative;
  options->objfind = NULL;

  /* pathchange left =NULL by default */
  options->change = diff_change;
  options->add_remove = diff_addremove;
  options->use_color = diff_use_color_default;
  options->detect_rename = diff_detect_rename_default;
  options->xdl_opts |= diff_algorithm;
  if (diff_indent_heuristic)
    DIFF_XDL_SET(options, INDENT_HEURISTIC);

  options->orderfile = xstrdup_or_null(diff_order_file_cfg);

  if (!options->flags.ignore_submodule_set)
    options->flags.ignore_untracked_in_submodules = 1;

  if (diff_no_prefix) {
    diff_set_noprefix(options);
  } else if (!diff_mnemonic_prefix) {
    diff_set_default_prefix(options);
  }

  options->color_moved = diff_color_moved_default;
  options->color_moved_ws_handling = diff_color_moved_ws_default;
}

static const char diff_status_letters[] = {
  DIFF_STATUS_ADDED,
  DIFF_STATUS_COPIED,
  DIFF_STATUS_DELETED,
  DIFF_STATUS_MODIFIED,
  DIFF_STATUS_RENAMED,
  DIFF_STATUS_TYPE_CHANGED,
  DIFF_STATUS_UNKNOWN,
  DIFF_STATUS_UNMERGED,
  DIFF_STATUS_FILTER_AON,
  DIFF_STATUS_FILTER_BROKEN,
  '\0',
};

static unsigned int filter_bit['Z' + 1];

static void prepare_filter_bits(void)
{
  int i;

  if (!filter_bit[DIFF_STATUS_ADDED]) {
    for (i = 0; diff_status_letters[i]; i++)
      filter_bit[(int) diff_status_letters[i]] = (1 << i);
  }
}

static unsigned filter_bit_tst(char status, const struct diff_options *opt)
{
  return opt->filter & filter_bit[(int) status];
}

unsigned diff_filter_bit(char status)
{
  prepare_filter_bits();
  return filter_bit[(int) status];
}

int diff_check_follow_pathspec(struct pathspec *ps, int die_on_error)
{
  unsigned forbidden_magic;

  if (ps->nr != 1) {
    if (die_on_error)
      die(_("--follow requires exactly one pathspec"));
    return 0;
  }

  forbidden_magic = ps->items[0].magic & ~(PATHSPEC_FROMTOP |
             PATHSPEC_LITERAL);
  if (forbidden_magic) {
    if (die_on_error) {
      struct strbuf sb = STRBUF_INIT;
      pathspec_magic_names(forbidden_magic, &sb);
      die(_("pathspec magic not supported by --follow: %s"),
          sb.buf);
    }
    return 0;
  }

  return 1;
}

void diff_setup_done(struct diff_options *options)
{
  unsigned check_mask = DIFF_FORMAT_NAME |
            DIFF_FORMAT_NAME_STATUS |
            DIFF_FORMAT_CHECKDIFF |
            DIFF_FORMAT_NO_OUTPUT;
  /*
   * This must be signed because we're comparing against a potentially
   * negative value.
   */
  const int hexsz = the_hash_algo->hexsz;

  if (options->set_default)
    options->set_default(options);

  if (HAS_MULTI_BITS(options->output_format & check_mask))
    die(_("options '%s', '%s', '%s', and '%s' cannot be used together"),
      "--name-only", "--name-status", "--check", "-s");

  if (HAS_MULTI_BITS(options->pickaxe_opts & DIFF_PICKAXE_KINDS_MASK))
    die(_("options '%s', '%s', and '%s' cannot be used together"),
      "-G", "-S", "--find-object");

  if (HAS_MULTI_BITS(options->pickaxe_opts & DIFF_PICKAXE_KINDS_G_REGEX_MASK))
    die(_("options '%s' and '%s' cannot be used together, use '%s' with '%s'"),
      "-G", "--pickaxe-regex", "--pickaxe-regex", "-S");

  if (HAS_MULTI_BITS(options->pickaxe_opts & DIFF_PICKAXE_KINDS_ALL_OBJFIND_MASK))
    die(_("options '%s' and '%s' cannot be used together, use '%s' with '%s' and '%s'"),
      "--pickaxe-all", "--find-object", "--pickaxe-all", "-G", "-S");

  /*
   * Most of the time we can say "there are changes"
   * only by checking if there are changed paths, but
   * --ignore-whitespace* options force us to look
   * inside contents.
   */

  if ((options->xdl_opts & XDF_WHITESPACE_FLAGS) ||
      options->ignore_regex_nr)
    options->flags.diff_from_contents = 1;
  else
    options->flags.diff_from_contents = 0;

  if (options->flags.find_copies_harder)
    options->detect_rename = DIFF_DETECT_COPY;

  if (!options->flags.relative_name)
    options->prefix = NULL;
  if (options->prefix)
    options->prefix_length = strlen(options->prefix);
  else
    options->prefix_length = 0;

  /*
   * --name-only, --name-status, --checkdiff, and -s
   * turn other output format off.
   */
  if (options->output_format & (DIFF_FORMAT_NAME |
              DIFF_FORMAT_NAME_STATUS |
              DIFF_FORMAT_CHECKDIFF |
              DIFF_FORMAT_NO_OUTPUT))
    options->output_format &= ~(DIFF_FORMAT_RAW |
              DIFF_FORMAT_NUMSTAT |
              DIFF_FORMAT_DIFFSTAT |
              DIFF_FORMAT_SHORTSTAT |
              DIFF_FORMAT_DIRSTAT |
              DIFF_FORMAT_SUMMARY |
              DIFF_FORMAT_PATCH);

  /*
   * These cases always need recursive; we do not drop caller-supplied
   * recursive bits for other formats here.
   */
  if (options->output_format & (DIFF_FORMAT_PATCH |
              DIFF_FORMAT_NUMSTAT |
              DIFF_FORMAT_DIFFSTAT |
              DIFF_FORMAT_SHORTSTAT |
              DIFF_FORMAT_DIRSTAT |
              DIFF_FORMAT_SUMMARY |
              DIFF_FORMAT_CHECKDIFF))
    options->flags.recursive = 1;
  /*
   * Also pickaxe would not work very well if you do not say recursive
   */
  if (options->pickaxe_opts & DIFF_PICKAXE_KINDS_MASK)
    options->flags.recursive = 1;
  /*
   * When patches are generated, submodules diffed against the work tree
   * must be checked for dirtiness too so it can be shown in the output
   */
  if (options->output_format & DIFF_FORMAT_PATCH)
    options->flags.dirty_submodules = 1;

  if (options->detect_rename && options->rename_limit < 0)
    options->rename_limit = diff_rename_limit_default;
  if (hexsz < options->abbrev)
    options->abbrev = hexsz; /* full */

  /*
   * It does not make sense to show the first hit we happened
   * to have found.  It does not make sense not to return with
   * exit code in such a case either.
   */
  if (options->flags.quick) {
    options->output_format = DIFF_FORMAT_NO_OUTPUT;
    options->flags.exit_with_status = 1;
    options->detect_rename = 0;
    options->flags.find_copies_harder = 0;
  }

  /*
   * External diffs could declare non-identical contents equal
   * (think diff --ignore-space-change).
   */
  if (options->flags.allow_external && options->flags.exit_with_status)
    options->flags.diff_from_contents = 1;

  options->diff_path_counter = 0;

  if (options->flags.follow_renames)
    diff_check_follow_pathspec(&options->pathspec, 1);

  if (options->flags.allow_external && external_diff())
    options->color_moved = 0;

  if (options->filter_not) {
    if (!options->filter)
      options->filter = ~filter_bit[DIFF_STATUS_FILTER_AON];
    options->filter &= ~options->filter_not;
  }

  if (options->pathspec.has_wildcard && options->max_depth_valid)
    die("max-depth cannot be used with wildcard pathspecs");
}

int parse_long_opt(const char *opt, const char **argv,
       const char **optarg)
{
  const char *arg = argv[0];
  if (!skip_prefix(arg, "--", &arg))
    return 0;
  if (!skip_prefix(arg, opt, &arg))
    return 0;
  if (*arg == '=') { /* stuck form: --option=value */
    *optarg = arg + 1;
    return 1;
  }
  if (*arg != '\0')
    return 0;
  /* separate form: --option value */
  if (!argv[1])
    die("Option '--%s' requires a value", opt);
  *optarg = argv[1];
  return 2;
}

static int diff_opt_stat(const struct option *opt, const char *value, int unset)
{
  struct diff_options *options = opt->value;
  int width = options->stat_width;
  int name_width = options->stat_name_width;
  int graph_width = options->stat_graph_width;
  int count = options->stat_count;
  char *end;

  BUG_ON_OPT_NEG(unset);

  if (!strcmp(opt->long_name, "stat")) {
    if (value) {
      width = strtoul(value, &end, 10);
      if (*end == ',')
        name_width = strtoul(end+1, &end, 10);
      if (*end == ',')
        count = strtoul(end+1, &end, 10);
      if (*end)
        return error(_("invalid --stat value: %s"), value);
    }
  } else if (!strcmp(opt->long_name, "stat-width")) {
    width = strtoul(value, &end, 10);
    if (*end)
      return error(_("%s expects a numerical value"),
             opt->long_name);
  } else if (!strcmp(opt->long_name, "stat-name-width")) {
    name_width = strtoul(value, &end, 10);
    if (*end)
      return error(_("%s expects a numerical value"),
             opt->long_name);
  } else if (!strcmp(opt->long_name, "stat-graph-width")) {
    graph_width = strtoul(value, &end, 10);
    if (*end)
      return error(_("%s expects a numerical value"),
             opt->long_name);
  } else if (!strcmp(opt->long_name, "stat-count")) {
    count = strtoul(value, &end, 10);
    if (*end)
      return error(_("%s expects a numerical value"),
             opt->long_name);
  } else
    BUG("%s should not get here", opt->long_name);

  options->output_format &= ~DIFF_FORMAT_NO_OUTPUT;
  options->output_format |= DIFF_FORMAT_DIFFSTAT;
  options->stat_name_width = name_width;
  options->stat_graph_width = graph_width;
  options->stat_width = width;
  options->stat_count = count;
  return 0;
}

static int parse_dirstat_opt(struct diff_options *options, const char *params)
{
  struct strbuf errmsg = STRBUF_INIT;
  if (parse_dirstat_params(options, params, &errmsg))
    die(_("Failed to parse --dirstat/-X option parameter:\n%s"),
        errmsg.buf);
  strbuf_release(&errmsg);
  /*
   * The caller knows a dirstat-related option is given from the command
   * line; allow it to say "return this_function();"
   */
  options->output_format &= ~DIFF_FORMAT_NO_OUTPUT;
  options->output_format |= DIFF_FORMAT_DIRSTAT;
  return 1;
}

static int diff_opt_diff_filter(const struct option *option,
        const char *optarg, int unset)
{
  struct diff_options *opt = option->value;
  int i, optch;

  BUG_ON_OPT_NEG(unset);
  prepare_filter_bits();

  for (i = 0; (optch = optarg[i]) != '\0'; i++) {
    unsigned int bit;
    int negate;

    if ('a' <= optch && optch <= 'z') {
      negate = 1;
      optch = toupper(optch);
    } else {
      negate = 0;
    }

    bit = (0 <= optch && optch <= 'Z') ? filter_bit[optch] : 0;
    if (!bit)
      return error(_("unknown change class '%c' in --diff-filter=%s"),
             optarg[i], optarg);
    if (negate)
      opt->filter_not |= bit;
    else
      opt->filter |= bit;
  }
  return 0;
}

static void enable_patch_output(int *fmt)
{
  *fmt &= ~DIFF_FORMAT_NO_OUTPUT;
  *fmt |= DIFF_FORMAT_PATCH;
}

static int diff_opt_ws_error_highlight(const struct option *option,
               const char *arg, int unset)
{
  struct diff_options *opt = option->value;
  int val = parse_ws_error_highlight(arg);

  BUG_ON_OPT_NEG(unset);
  if (val < 0)
    return error(_("unknown value after ws-error-highlight=%.*s"),
           -1 - val, arg);
  opt->ws_error_highlight = val;
  return 0;
}

static int diff_opt_find_object(const struct option *option,
        const char *arg, int unset)
{
  struct diff_options *opt = option->value;
  struct object_id oid;

  BUG_ON_OPT_NEG(unset);
  if (!startup_info->have_repository)
    return error(_("--find-object requires a git repository"));
  if (repo_get_oid(the_repository, arg, &oid))
    return error(_("unable to resolve '%s'"), arg);

  if (!opt->objfind)
    CALLOC_ARRAY(opt->objfind, 1);

  opt->pickaxe_opts |= DIFF_PICKAXE_KIND_OBJFIND;
  opt->flags.recursive = 1;
  opt->flags.tree_in_recursive = 1;
  oidset_insert(opt->objfind, &oid);
  return 0;
}

static int diff_opt_anchored(const struct option *opt,
           const char *arg, int unset)
{
  struct diff_options *options = opt->value;

  BUG_ON_OPT_NEG(unset);
  options->xdl_opts = DIFF_WITH_ALG(options, PATIENCE_DIFF);
  ALLOC_GROW(options->anchors, options->anchors_nr + 1,
       options->anchors_alloc);
  options->anchors[options->anchors_nr++] = xstrdup(arg);
  return 0;
}

static int diff_opt_binary(const struct option *opt,
         const char *arg, int unset)
{
  struct diff_options *options = opt->value;

  BUG_ON_OPT_NEG(unset);
  BUG_ON_OPT_ARG(arg);
  enable_patch_output(&options->output_format);
  options->flags.binary = 1;
  return 0;
}

static int diff_opt_break_rewrites(const struct option *opt,
           const char *arg, int unset)
{
  int *break_opt = opt->value;
  int opt1, opt2;

  BUG_ON_OPT_NEG(unset);
  if (!arg)
    arg = "";
  opt1 = parse_rename_score(&arg);
  if (*arg == 0)
    opt2 = 0;
  else if (*arg != '/')
    return error(_("%s expects <n>/<m> form"), opt->long_name);
  else {
    arg++;
    opt2 = parse_rename_score(&arg);
  }
  if (*arg != 0)
    return error(_("%s expects <n>/<m> form"), opt->long_name);
  *break_opt = opt1 | (opt2 << 16);
  return 0;
}

static int diff_opt_char(const struct option *opt,
       const char *arg, int unset)
{
  char *value = opt->value;

  BUG_ON_OPT_NEG(unset);
  if (arg[1])
    return error(_("%s expects a character, got '%s'"),
           opt->long_name, arg);
  *value = arg[0];
  return 0;
}

static int diff_opt_color_moved(const struct option *opt,
        const char *arg, int unset)
{
  struct diff_options *options = opt->value;

  if (unset) {
    options->color_moved = COLOR_MOVED_NO;
  } else if (!arg) {
    if (diff_color_moved_default)
      options->color_moved = diff_color_moved_default;
    if (options->color_moved == COLOR_MOVED_NO)
      options->color_moved = COLOR_MOVED_DEFAULT;
  } else {
    int cm = parse_color_moved(arg);
    if (cm < 0)
      return error(_("bad --color-moved argument: %s"), arg);
    options->color_moved = cm;
  }
  return 0;
}

static int diff_opt_color_moved_ws(const struct option *opt,
           const char *arg, int unset)
{
  struct diff_options *options = opt->value;
  unsigned cm;

  if (unset) {
    options->color_moved_ws_handling = 0;
    return 0;
  }

  cm = parse_color_moved_ws(arg);
  if (cm & COLOR_MOVED_WS_ERROR)
    return error(_("invalid mode '%s' in --color-moved-ws"), arg);
  options->color_moved_ws_handling = cm;
  return 0;
}

static int diff_opt_color_words(const struct option *opt,
        const char *arg, int unset)
{
  struct diff_options *options = opt->value;

  BUG_ON_OPT_NEG(unset);
  options->use_color = GIT_COLOR_ALWAYS;
  options->word_diff = DIFF_WORDS_COLOR;
  options->word_regex = arg;
  return 0;
}

static int diff_opt_compact_summary(const struct option *opt,
            const char *arg, int unset)
{
  struct diff_options *options = opt->value;

  BUG_ON_OPT_ARG(arg);
  if (unset) {
    options->flags.stat_with_summary = 0;
  } else {
    options->flags.stat_with_summary = 1;
    options->output_format &= ~DIFF_FORMAT_NO_OUTPUT;
    options->output_format |= DIFF_FORMAT_DIFFSTAT;
  }
  return 0;
}

static int diff_opt_diff_algorithm(const struct option *opt,
           const char *arg, int unset)
{
  struct diff_options *options = opt->value;

  BUG_ON_OPT_NEG(unset);

  if (set_diff_algorithm(options, arg))
    return error(_("option diff-algorithm accepts \"myers\", "
             "\"minimal\", \"patience\" and \"histogram\""));

  options->ignore_driver_algorithm = 1;

  return 0;
}

static int diff_opt_diff_algorithm_no_arg(const struct option *opt,
           const char *arg, int unset)
{
  struct diff_options *options = opt->value;

  BUG_ON_OPT_NEG(unset);
  BUG_ON_OPT_ARG(arg);

  if (set_diff_algorithm(options, opt->long_name))
    BUG("available diff algorithms include \"myers\", "
             "\"minimal\", \"patience\" and \"histogram\"");

  options->ignore_driver_algorithm = 1;

  return 0;
}

static int diff_opt_dirstat(const struct option *opt,
          const char *arg, int unset)
{
  struct diff_options *options = opt->value;

  BUG_ON_OPT_NEG(unset);
  if (!strcmp(opt->long_name, "cumulative")) {
    if (arg)
      BUG("how come --cumulative take a value?");
    arg = "cumulative";
  } else if (!strcmp(opt->long_name, "dirstat-by-file"))
    parse_dirstat_opt(options, "files");
  parse_dirstat_opt(options, arg ? arg : "");
  return 0;
}

static int diff_opt_find_copies(const struct option *opt,
        const char *arg, int unset)
{
  struct diff_options *options = opt->value;

  BUG_ON_OPT_NEG(unset);
  if (!arg)
    arg = "";
  options->rename_score = parse_rename_score(&arg);
  if (*arg != 0)
    return error(_("invalid argument to %s"), opt->long_name);

  if (options->detect_rename == DIFF_DETECT_COPY)
    options->flags.find_copies_harder = 1;
  else
    options->detect_rename = DIFF_DETECT_COPY;

  return 0;
}

static int diff_opt_find_renames(const struct option *opt,
         const char *arg, int unset)
{
  struct diff_options *options = opt->value;

  BUG_ON_OPT_NEG(unset);
  if (!arg)
    arg = "";
  options->rename_score = parse_rename_score(&arg);
  if (*arg != 0)
    return error(_("invalid argument to %s"), opt->long_name);

  options->detect_rename = DIFF_DETECT_RENAME;
  return 0;
}

static int diff_opt_follow(const struct option *opt,
         const char *arg, int unset)
{
  struct diff_options *options = opt->value;

  BUG_ON_OPT_ARG(arg);
  if (unset) {
    options->flags.follow_renames = 0;
    options->flags.default_follow_renames = 0;
  } else {
    options->flags.follow_renames = 1;
  }
  return 0;
}

static int diff_opt_ignore_submodules(const struct option *opt,
              const char *arg, int unset)
{
  struct diff_options *options = opt->value;

  BUG_ON_OPT_NEG(unset);
  if (!arg)
    arg = "all";
  options->flags.override_submodule_config = 1;
  handle_ignore_submodules_arg(options, arg);
  return 0;
}

static int diff_opt_line_prefix(const struct option *opt,
        const char *optarg, int unset)
{
  struct diff_options *options = opt->value;

  BUG_ON_OPT_NEG(unset);
  options->line_prefix = optarg;
  graph_setup_line_prefix(options);
  return 0;
}

static int diff_opt_no_prefix(const struct option *opt,
            const char *optarg, int unset)
{
  struct diff_options *options = opt->value;

  BUG_ON_OPT_NEG(unset);
  BUG_ON_OPT_ARG(optarg);
  diff_set_noprefix(options);
  return 0;
}

static int diff_opt_default_prefix(const struct option *opt,
           const char *optarg, int unset)
{
  struct diff_options *options = opt->value;

  BUG_ON_OPT_NEG(unset);
  BUG_ON_OPT_ARG(optarg);
  FREE_AND_NULL(diff_src_prefix);
  FREE_AND_NULL(diff_dst_prefix);
  diff_set_default_prefix(options);
  return 0;
}

static enum parse_opt_result diff_opt_output(struct parse_opt_ctx_t *ctx,
               const struct option *opt,
               const char *arg, int unset)
{
  struct diff_options *options = opt->value;
  char *path;

  BUG_ON_OPT_NEG(unset);
  path = prefix_filename(ctx->prefix, arg);
  options->file = xfopen(path, "w");
  options->close_file = 1;
  if (options->use_color != GIT_COLOR_ALWAYS)
    options->use_color = GIT_COLOR_NEVER;
  free(path);
  return 0;
}

static int diff_opt_patience(const struct option *opt,
           const char *arg, int unset)
{
  struct diff_options *options = opt->value;
  int i;

  BUG_ON_OPT_NEG(unset);
  BUG_ON_OPT_ARG(arg);
  /*
   * Both --patience and --anchored use PATIENCE_DIFF
   * internally, so remove any anchors previously
   * specified.
   */
  for (i = 0; i < options->anchors_nr; i++)
    free(options->anchors[i]);
  options->anchors_nr = 0;
  options->ignore_driver_algorithm = 1;

  return set_diff_algorithm(options, "patience");
}

static int diff_opt_ignore_regex(const struct option *opt,
         const char *arg, int unset)
{
  struct diff_options *options = opt->value;
  regex_t *regex;

  BUG_ON_OPT_NEG(unset);

  regex = xmalloc(sizeof(*regex));
  if (regcomp(regex, arg, REG_EXTENDED | REG_NEWLINE)) {
    free(regex);
    return error(_("invalid regex given to -I: '%s'"), arg);
  }

  ALLOC_GROW(options->ignore_regex, options->ignore_regex_nr + 1,
       options->ignore_regex_alloc);
  options->ignore_regex[options->ignore_regex_nr++] = regex;
  return 0;
}

static int diff_opt_pickaxe_regex(const struct option *opt,
          const char *arg, int unset)
{
  struct diff_options *options = opt->value;

  BUG_ON_OPT_NEG(unset);
  options->pickaxe = arg;
  options->pickaxe_opts |= DIFF_PICKAXE_KIND_G;
  if (arg && !*arg)
    return error(_("-G requires a non-empty argument"));
  return 0;
}

static int diff_opt_pickaxe_string(const struct option *opt,
           const char *arg, int unset)
{
  struct diff_options *options = opt->value;

  BUG_ON_OPT_NEG(unset);
  options->pickaxe = arg;
  options->pickaxe_opts |= DIFF_PICKAXE_KIND_S;
  if (arg && !*arg)
    return error(_("-S requires a non-empty argument"));
  return 0;
}

static int diff_opt_relative(const struct option *opt,
           const char *arg, int unset)
{
  struct diff_options *options = opt->value;

  options->flags.relative_name = !unset;
  if (arg)
    options->prefix = arg;
  return 0;
}

static int diff_opt_submodule(const struct option *opt,
            const char *arg, int unset)
{
  struct diff_options *options = opt->value;

  BUG_ON_OPT_NEG(unset);
  if (!arg)
    arg = "log";
  if (parse_submodule_params(options, arg))
    return error(_("failed to parse --submodule option parameter: '%s'"),
           arg);
  return 0;
}

static int diff_opt_textconv(const struct option *opt,
           const char *arg, int unset)
{
  struct diff_options *options = opt->value;

  BUG_ON_OPT_ARG(arg);
  if (unset) {
    options->flags.allow_textconv = 0;
  } else {
    options->flags.allow_textconv = 1;
    options->flags.textconv_set_via_cmdline = 1;
  }
  return 0;
}

static int diff_opt_unified(const struct option *opt,
          const char *arg, int unset)
{
  struct diff_options *options = opt->value;
  char *s;

  BUG_ON_OPT_NEG(unset);

  if (arg) {
    long val = strtol(arg, &s, 10);
    if (*s)
      return error(_("%s expects a numerical value"), "--unified");
    if (val < 0)
      return error(_("%s expects a non-negative integer"), "--unified");
    options->context = val;
  }
  enable_patch_output(&options->output_format);

  return 0;
}

static int diff_opt_word_diff(const struct option *opt,
            const char *arg, int unset)
{
  struct diff_options *options = opt->value;

  BUG_ON_OPT_NEG(unset);
  if (arg) {
    if (!strcmp(arg, "plain"))
      options->word_diff = DIFF_WORDS_PLAIN;
    else if (!strcmp(arg, "color")) {
      options->use_color = GIT_COLOR_ALWAYS;
      options->word_diff = DIFF_WORDS_COLOR;
    }
    else if (!strcmp(arg, "porcelain"))
      options->word_diff = DIFF_WORDS_PORCELAIN;
    else if (!strcmp(arg, "none"))
      options->word_diff = DIFF_WORDS_NONE;
    else
      return error(_("bad --word-diff argument: %s"), arg);
  } else {
    if (options->word_diff == DIFF_WORDS_NONE)
      options->word_diff = DIFF_WORDS_PLAIN;
  }
  return 0;
}

static int diff_opt_word_diff_regex(const struct option *opt,
            const char *arg, int unset)
{
  struct diff_options *options = opt->value;

  BUG_ON_OPT_NEG(unset);
  if (options->word_diff == DIFF_WORDS_NONE)
    options->word_diff = DIFF_WORDS_PLAIN;
  options->word_regex = arg;
  return 0;
}

static int diff_opt_rotate_to(const struct option *opt, const char *arg, int unset)
{
  struct diff_options *options = opt->value;

  BUG_ON_OPT_NEG(unset);
  if (!strcmp(opt->long_name, "skip-to"))
    options->skip_instead_of_rotate = 1;
  else
    options->skip_instead_of_rotate = 0;
  options->rotate_to = arg;
  return 0;
}

static int diff_opt_max_depth(const struct option *opt,
            const char *arg, int unset)
{
  struct diff_options *options = opt->value;

  BUG_ON_OPT_NEG(unset);

  if (!git_parse_int(arg, &options->max_depth))
    return error(_("invalid value for '%s': '%s'"),
           "--max-depth", arg);

  options->flags.recursive = 1;
  options->max_depth_valid = options->max_depth >= 0;

  return 0;
}

/*
 * Consider adding new flags to __git_diff_common_options
 * in contrib/completion/git-completion.bash
 */
struct option *add_diff_options(const struct option *opts,
        struct diff_options *options)
{
  struct option parseopts[] = {
    OPT_GROUP(N_("Diff output format options")),
    OPT_BITOP('p', "patch", &options->output_format,
        N_("generate patch"),
        DIFF_FORMAT_PATCH, DIFF_FORMAT_NO_OUTPUT),
    OPT_SET_INT('s', "no-patch", &options->output_format,
          N_("suppress diff output"), DIFF_FORMAT_NO_OUTPUT),
    OPT_BITOP('u', NULL, &options->output_format,
        N_("generate patch"),
        DIFF_FORMAT_PATCH, DIFF_FORMAT_NO_OUTPUT),
    OPT_CALLBACK_F('U', "unified", options, N_("<n>"),
             N_("generate diffs with <n> lines context"),
             PARSE_OPT_NONEG | PARSE_OPT_OPTARG, diff_opt_unified),
    OPT_BOOL('W', "function-context", &options->flags.funccontext,
       N_("generate diffs with <n> lines context")),
    OPT_BITOP(0, "raw", &options->output_format,
        N_("generate the diff in raw format"),
        DIFF_FORMAT_RAW, DIFF_FORMAT_NO_OUTPUT),
    OPT_BITOP(0, "patch-with-raw", &options->output_format,
        N_("synonym for '-p --raw'"),
        DIFF_FORMAT_PATCH | DIFF_FORMAT_RAW,
        DIFF_FORMAT_NO_OUTPUT),
    OPT_BITOP(0, "patch-with-stat", &options->output_format,
        N_("synonym for '-p --stat'"),
        DIFF_FORMAT_PATCH | DIFF_FORMAT_DIFFSTAT,
        DIFF_FORMAT_NO_OUTPUT),
    OPT_BITOP(0, "numstat", &options->output_format,
        N_("machine friendly --stat"),
        DIFF_FORMAT_NUMSTAT, DIFF_FORMAT_NO_OUTPUT),
    OPT_BITOP(0, "shortstat", &options->output_format,
        N_("output only the last line of --stat"),
        DIFF_FORMAT_SHORTSTAT, DIFF_FORMAT_NO_OUTPUT),
    OPT_CALLBACK_F('X', "dirstat", options, N_("<param1>,<param2>..."),
             N_("output the distribution of relative amount of changes for each sub-directory"),
             PARSE_OPT_NONEG | PARSE_OPT_OPTARG,
             diff_opt_dirstat),
    OPT_CALLBACK_F(0, "cumulative", options, NULL,
             N_("synonym for --dirstat=cumulative"),
             PARSE_OPT_NONEG | PARSE_OPT_NOARG,
             diff_opt_dirstat),
    OPT_CALLBACK_F(0, "dirstat-by-file", options, N_("<param1>,<param2>..."),
             N_("synonym for --dirstat=files,<param1>,<param2>..."),
             PARSE_OPT_NONEG | PARSE_OPT_OPTARG,
             diff_opt_dirstat),
    OPT_BIT_F(0, "check", &options->output_format,
        N_("warn if changes introduce conflict markers or whitespace errors"),
        DIFF_FORMAT_CHECKDIFF, PARSE_OPT_NONEG),
    OPT_BITOP(0, "summary", &options->output_format,
        N_("condensed summary such as creations, renames and mode changes"),
        DIFF_FORMAT_SUMMARY, DIFF_FORMAT_NO_OUTPUT),
    OPT_BIT_F(0, "name-only", &options->output_format,
        N_("show only names of changed files"),
        DIFF_FORMAT_NAME, PARSE_OPT_NONEG),
    OPT_BIT_F(0, "name-status", &options->output_format,
        N_("show only names and status of changed files"),
        DIFF_FORMAT_NAME_STATUS, PARSE_OPT_NONEG),
    OPT_CALLBACK_F(0, "stat", options, N_("<width>[,<name-width>[,<count>]]"),
             N_("generate diffstat"),
             PARSE_OPT_NONEG | PARSE_OPT_OPTARG, diff_opt_stat),
    OPT_CALLBACK_F(0, "stat-width", options, N_("<width>"),
             N_("generate diffstat with a given width"),
             PARSE_OPT_NONEG, diff_opt_stat),
    OPT_CALLBACK_F(0, "stat-name-width", options, N_("<width>"),
             N_("generate diffstat with a given name width"),
             PARSE_OPT_NONEG, diff_opt_stat),
    OPT_CALLBACK_F(0, "stat-graph-width", options, N_("<width>"),
             N_("generate diffstat with a given graph width"),
             PARSE_OPT_NONEG, diff_opt_stat),
    OPT_CALLBACK_F(0, "stat-count", options, N_("<count>"),
             N_("generate diffstat with limited lines"),
             PARSE_OPT_NONEG, diff_opt_stat),
    OPT_CALLBACK_F(0, "compact-summary", options, NULL,
             N_("generate compact summary in diffstat"),
             PARSE_OPT_NOARG, diff_opt_compact_summary),
    OPT_CALLBACK_F(0, "binary", options, NULL,
             N_("output a binary diff that can be applied"),
             PARSE_OPT_NONEG | PARSE_OPT_NOARG, diff_opt_binary),
    OPT_BOOL(0, "full-index", &options->flags.full_index,
       N_("show full pre- and post-image object names on the \"index\" lines")),
    OPT_COLOR_FLAG(0, "color", &options->use_color,
             N_("show colored diff")),
    OPT_CALLBACK_F(0, "ws-error-highlight", options, N_("<kind>"),
             N_("highlight whitespace errors in the 'context', 'old' or 'new' lines in the diff"),
             PARSE_OPT_NONEG, diff_opt_ws_error_highlight),
    OPT_SET_INT('z', NULL, &options->line_termination,
          N_("do not munge pathnames and use NULs as output field terminators in --raw or --numstat"),
          0),
    OPT__ABBREV(&options->abbrev),
    OPT_STRING_F(0, "src-prefix", &options->a_prefix, N_("<prefix>"),
           N_("show the given source prefix instead of \"a/\""),
           PARSE_OPT_NONEG),
    OPT_STRING_F(0, "dst-prefix", &options->b_prefix, N_("<prefix>"),
           N_("show the given destination prefix instead of \"b/\""),
           PARSE_OPT_NONEG),
    OPT_CALLBACK_F(0, "line-prefix", options, N_("<prefix>"),
             N_("prepend an additional prefix to every line of output"),
             PARSE_OPT_NONEG, diff_opt_line_prefix),
    OPT_CALLBACK_F(0, "no-prefix", options, NULL,
             N_("do not show any source or destination prefix"),
             PARSE_OPT_NONEG | PARSE_OPT_NOARG, diff_opt_no_prefix),
    OPT_CALLBACK_F(0, "default-prefix", options, NULL,
             N_("use default prefixes a/ and b/"),
             PARSE_OPT_NONEG | PARSE_OPT_NOARG, diff_opt_default_prefix),
    OPT_UNSIGNED(0, "inter-hunk-context", &options->interhunkcontext,
           N_("show context between diff hunks up to the specified number of lines")),
    OPT_CALLBACK_F(0, "output-indicator-new",
             &options->output_indicators[OUTPUT_INDICATOR_NEW],
             N_("<char>"),
             N_("specify the character to indicate a new line instead of '+'"),
             PARSE_OPT_NONEG, diff_opt_char),
    OPT_CALLBACK_F(0, "output-indicator-old",
             &options->output_indicators[OUTPUT_INDICATOR_OLD],
             N_("<char>"),
             N_("specify the character to indicate an old line instead of '-'"),
             PARSE_OPT_NONEG, diff_opt_char),
    OPT_CALLBACK_F(0, "output-indicator-context",
             &options->output_indicators[OUTPUT_INDICATOR_CONTEXT],
             N_("<char>"),
             N_("specify the character to indicate a context instead of ' '"),
             PARSE_OPT_NONEG, diff_opt_char),

    OPT_GROUP(N_("Diff rename options")),
    OPT_CALLBACK_F('B', "break-rewrites", &options->break_opt, N_("<n>[/<m>]"),
             N_("break complete rewrite changes into pairs of delete and create"),
             PARSE_OPT_NONEG | PARSE_OPT_OPTARG,
             diff_opt_break_rewrites),
    OPT_CALLBACK_F('M', "find-renames", options, N_("<n>"),
             N_("detect renames"),
             PARSE_OPT_NONEG | PARSE_OPT_OPTARG,
             diff_opt_find_renames),
    OPT_SET_INT_F('D', "irreversible-delete", &options->irreversible_delete,
            N_("omit the preimage for deletes"),
            1, PARSE_OPT_NONEG),
    OPT_CALLBACK_F('C', "find-copies", options, N_("<n>"),
             N_("detect copies"),
             PARSE_OPT_NONEG | PARSE_OPT_OPTARG,
             diff_opt_find_copies),
    OPT_BOOL(0, "find-copies-harder", &options->flags.find_copies_harder,
       N_("use unmodified files as source to find copies")),
    OPT_SET_INT_F(0, "no-renames", &options->detect_rename,
            N_("disable rename detection"),
            0, PARSE_OPT_NONEG),
    OPT_BOOL(0, "rename-empty", &options->flags.rename_empty,
       N_("use empty blobs as rename source")),
    OPT_CALLBACK_F(0, "follow", options, NULL,
             N_("continue listing the history of a file beyond renames"),
             PARSE_OPT_NOARG, diff_opt_follow),
    OPT_INTEGER('l', NULL, &options->rename_limit,
          N_("limit to cheap rename/copy detection if the number of rename/copy targets exceeds this value")),

    OPT_GROUP(N_("Diff algorithm options")),
    OPT_CALLBACK_F(0, "minimal", options, NULL,
             N_("produce the smallest possible diff"),
             PARSE_OPT_NONEG | PARSE_OPT_NOARG,
             diff_opt_diff_algorithm_no_arg),
    OPT_BIT_F('w', "ignore-all-space", &options->xdl_opts,
        N_("ignore whitespace when comparing lines"),
        XDF_IGNORE_WHITESPACE, PARSE_OPT_NONEG),
    OPT_BIT_F('b', "ignore-space-change", &options->xdl_opts,
        N_("ignore changes in amount of whitespace"),
        XDF_IGNORE_WHITESPACE_CHANGE, PARSE_OPT_NONEG),
    OPT_BIT_F(0, "ignore-space-at-eol", &options->xdl_opts,
        N_("ignore changes in whitespace at EOL"),
        XDF_IGNORE_WHITESPACE_AT_EOL, PARSE_OPT_NONEG),
    OPT_BIT_F(0, "ignore-cr-at-eol", &options->xdl_opts,
        N_("ignore carrier-return at the end of line"),
        XDF_IGNORE_CR_AT_EOL, PARSE_OPT_NONEG),
    OPT_BIT_F(0, "ignore-blank-lines", &options->xdl_opts,
        N_("ignore changes whose lines are all blank"),
        XDF_IGNORE_BLANK_LINES, PARSE_OPT_NONEG),
    OPT_CALLBACK_F('I', "ignore-matching-lines", options, N_("<regex>"),
             N_("ignore changes whose all lines match <regex>"),
             0, diff_opt_ignore_regex),
    OPT_BIT(0, "indent-heuristic", &options->xdl_opts,
      N_("heuristic to shift diff hunk boundaries for easy reading"),
      XDF_INDENT_HEURISTIC),
    OPT_CALLBACK_F(0, "patience", options, NULL,
             N_("generate diff using the \"patience diff\" algorithm"),
             PARSE_OPT_NONEG | PARSE_OPT_NOARG,
             diff_opt_patience),
    OPT_CALLBACK_F(0, "histogram", options, NULL,
             N_("generate diff using the \"histogram diff\" algorithm"),
             PARSE_OPT_NONEG | PARSE_OPT_NOARG,
             diff_opt_diff_algorithm_no_arg),
    OPT_CALLBACK_F(0, "diff-algorithm", options, N_("<algorithm>"),
             N_("choose a diff algorithm"),
             PARSE_OPT_NONEG, diff_opt_diff_algorithm),
    OPT_CALLBACK_F(0, "anchored", options, N_("<text>"),
             N_("generate diff using the \"anchored diff\" algorithm"),
             PARSE_OPT_NONEG, diff_opt_anchored),
    OPT_CALLBACK_F(0, "word-diff", options, N_("<mode>"),
             N_("show word diff, using <mode> to delimit changed words"),
             PARSE_OPT_NONEG | PARSE_OPT_OPTARG, diff_opt_word_diff),
    OPT_CALLBACK_F(0, "word-diff-regex", options, N_("<regex>"),
             N_("use <regex> to decide what a word is"),
             PARSE_OPT_NONEG, diff_opt_word_diff_regex),
    OPT_CALLBACK_F(0, "color-words", options, N_("<regex>"),
             N_("equivalent to --word-diff=color --word-diff-regex=<regex>"),
             PARSE_OPT_NONEG | PARSE_OPT_OPTARG, diff_opt_color_words),
    OPT_CALLBACK_F(0, "color-moved", options, N_("<mode>"),
             N_("moved lines of code are colored differently"),
             PARSE_OPT_OPTARG, diff_opt_color_moved),
    OPT_CALLBACK_F(0, "color-moved-ws", options, N_("<mode>"),
             N_("how white spaces are ignored in --color-moved"),
             0, diff_opt_color_moved_ws),

    OPT_GROUP(N_("Other diff options")),
    OPT_CALLBACK_F(0, "relative", options, N_("<prefix>"),
             N_("when run from subdir, exclude changes outside and show relative paths"),
             PARSE_OPT_OPTARG,
             diff_opt_relative),
    OPT_BOOL('a', "text", &options->flags.text,
       N_("treat all files as text")),
    OPT_BOOL('R', NULL, &options->flags.reverse_diff,
       N_("swap two inputs, reverse the diff")),
    OPT_BOOL(0, "exit-code", &options->flags.exit_with_status,
       N_("exit with 1 if there were differences, 0 otherwise")),
    OPT_BOOL(0, "quiet", &options->flags.quick,
       N_("disable all output of the program")),
    OPT_BOOL(0, "ext-diff", &options->flags.allow_external,
       N_("allow an external diff helper to be executed")),
    OPT_CALLBACK_F(0, "textconv", options, NULL,
             N_("run external text conversion filters when comparing binary files"),
             PARSE_OPT_NOARG, diff_opt_textconv),
    OPT_CALLBACK_F(0, "ignore-submodules", options, N_("<when>"),
             N_("ignore changes to submodules in the diff generation"),
             PARSE_OPT_NONEG | PARSE_OPT_OPTARG,
             diff_opt_ignore_submodules),
    OPT_CALLBACK_F(0, "submodule", options, N_("<format>"),
             N_("specify how differences in submodules are shown"),
             PARSE_OPT_NONEG | PARSE_OPT_OPTARG,
             diff_opt_submodule),
    OPT_SET_INT_F(0, "ita-invisible-in-index", &options->ita_invisible_in_index,
            N_("hide 'git add -N' entries from the index"),
            1, PARSE_OPT_NONEG),
    OPT_SET_INT_F(0, "ita-visible-in-index", &options->ita_invisible_in_index,
            N_("treat 'git add -N' entries as real in the index"),
            0, PARSE_OPT_NONEG),
    OPT_CALLBACK_F('S', NULL, options, N_("<string>"),
             N_("look for differences that change the number of occurrences of the specified string"),
             0, diff_opt_pickaxe_string),
    OPT_CALLBACK_F('G', NULL, options, N_("<regex>"),
             N_("look for differences that change the number of occurrences of the specified regex"),
             0, diff_opt_pickaxe_regex),
    OPT_BIT_F(0, "pickaxe-all", &options->pickaxe_opts,
        N_("show all changes in the changeset with -S or -G"),
        DIFF_PICKAXE_ALL, PARSE_OPT_NONEG),
    OPT_BIT_F(0, "pickaxe-regex", &options->pickaxe_opts,
        N_("treat <string> in -S as extended POSIX regular expression"),
        DIFF_PICKAXE_REGEX, PARSE_OPT_NONEG),
    OPT_FILENAME('O', NULL, &options->orderfile,
           N_("control the order in which files appear in the output")),
    OPT_CALLBACK_F(0, "rotate-to", options, N_("<path>"),
             N_("show the change in the specified path first"),
             PARSE_OPT_NONEG, diff_opt_rotate_to),
    OPT_CALLBACK_F(0, "skip-to", options, N_("<path>"),
             N_("skip the output to the specified path"),
             PARSE_OPT_NONEG, diff_opt_rotate_to),
    OPT_CALLBACK_F(0, "find-object", options, N_("<object-id>"),
             N_("look for differences that change the number of occurrences of the specified object"),
             PARSE_OPT_NONEG, diff_opt_find_object),
    OPT_CALLBACK_F(0, "diff-filter", options, N_("[(A|C|D|M|R|T|U|X|B)...[*]]"),
             N_("select files by diff type"),
             PARSE_OPT_NONEG, diff_opt_diff_filter),
    OPT_CALLBACK_F(0, "max-depth", options, N_("<depth>"),
             N_("maximum tree depth to recurse"),
             PARSE_OPT_NONEG, diff_opt_max_depth),

    {
      .type = OPTION_CALLBACK,
      .long_name = "output",
      .value = options,
      .argh = N_("<file>"),
      .help = N_("output to a specific file"),
      .flags = PARSE_OPT_NONEG,
      .ll_callback = diff_opt_output,
    },
    OPT_END()
  };

  return parse_options_concat(opts, parseopts);
}

int diff_opt_parse(struct diff_options *options,
       const char **av, int ac, const char *prefix)
{
  struct option no_options[] = { OPT_END() };
  struct option *parseopts = add_diff_options(no_options, options);

  if (!prefix)
    prefix = "";

  ac = parse_options(ac, av, prefix, parseopts, NULL,
         PARSE_OPT_KEEP_DASHDASH |
         PARSE_OPT_KEEP_UNKNOWN_OPT |
         PARSE_OPT_NO_INTERNAL_HELP |
         PARSE_OPT_ONE_SHOT |
         PARSE_OPT_STOP_AT_NON_OPTION);
  free(parseopts);

  return ac;
}

int parse_rename_score(const char **cp_p)
{
  unsigned long num, scale;
  int ch, dot;
  const char *cp = *cp_p;

  num = 0;
  scale = 1;
  dot = 0;
  for (;;) {
    ch = *cp;
    if ( !dot && ch == '.' ) {
      scale = 1;
      dot = 1;
    } else if ( ch == '%' ) {
      scale = dot ? scale*100 : 100;
      cp++; /* % is always at the end */
      break;
    } else if ( ch >= '0' && ch <= '9' ) {
      if ( scale < 100000 ) {
        scale *= 10;
        num = (num*10) + (ch-'0');
      }
    } else {
      break;
    }
    cp++;
  }
  *cp_p = cp;

  /* user says num divided by scale and we say internally that
   * is MAX_SCORE * num / scale.
   */
  return (int)((num >= scale) ? MAX_SCORE : (MAX_SCORE * num / scale));
}

struct diff_queue_struct diff_queued_diff;

void diff_q(struct diff_queue_struct *queue, struct diff_filepair *dp)
{
  ALLOC_GROW(queue->queue, queue->nr + 1, queue->alloc);
  queue->queue[queue->nr++] = dp;
}

struct diff_filepair *diff_queue(struct diff_queue_struct *queue,
         struct diff_filespec *one,
         struct diff_filespec *two)
{
  struct diff_filepair *dp = xcalloc(1, sizeof(*dp));
  dp->one = one;
  dp->two = two;
  if (queue)
    diff_q(queue, dp);
  return dp;
}

void diff_free_filepair(struct diff_filepair *p)
{
  free_filespec(p->one);
  free_filespec(p->two);
  free(p);
}

void diff_queue_init(struct diff_queue_struct *q)
{
  struct diff_queue_struct blank = DIFF_QUEUE_INIT;
  memcpy(q, &blank, sizeof(*q));
}

void diff_queue_clear(struct diff_queue_struct *q)
{
  for (int i = 0; i < q->nr; i++)
    diff_free_filepair(q->queue[i]);
  free(q->queue);
  diff_queue_init(q);
}

const char *diff_aligned_abbrev(const struct object_id *oid, int len)
{
  int abblen;
  const char *abbrev;

  /* Do we want all 40 hex characters? */
  if (len == the_hash_algo->hexsz)
    return oid_to_hex(oid);

  /* An abbreviated value is fine, possibly followed by an ellipsis. */
  abbrev = diff_abbrev_oid(oid, len);

  if (!print_sha1_ellipsis())
    return abbrev;

  abblen = strlen(abbrev);

  /*
   * In well-behaved cases, where the abbreviated result is the
   * same as the requested length, append three dots after the
   * abbreviation (hence the whole logic is limited to the case
   * where abblen < 37); when the actual abbreviated result is a
   * bit longer than the requested length, we reduce the number
   * of dots so that they match the well-behaved ones.  However,
   * if the actual abbreviation is longer than the requested
   * length by more than three, we give up on aligning, and add
   * three dots anyway, to indicate that the output is not the
   * full object name.  Yes, this may be suboptimal, but this
   * appears only in "diff --raw --abbrev" output and it is not
   * worth the effort to change it now.  Note that this would
   * likely to work fine when the automatic sizing of default
   * abbreviation length is used--we would be fed -1 in "len" in
   * that case, and will end up always appending three-dots, but
   * the automatic sizing is supposed to give abblen that ensures
   * uniqueness across all objects (statistically speaking).
   */
  if (abblen < the_hash_algo->hexsz - 3) {
    static char hex[GIT_MAX_HEXSZ + 1];
    if (len < abblen && abblen <= len + 2)
      xsnprintf(hex, sizeof(hex), "%s%.*s", abbrev, len+3-abblen, "..");
    else
      xsnprintf(hex, sizeof(hex), "%s...", abbrev);
    return hex;
  }

  return oid_to_hex(oid);
}

static void diff_flush_raw(struct diff_filepair *p, struct diff_options *opt)
{
  int line_termination = opt->line_termination;
  int inter_name_termination = line_termination ? '\t' : '\0';

  fprintf(opt->file, "%s", diff_line_prefix(opt));
  if (!(opt->output_format & DIFF_FORMAT_NAME_STATUS)) {
    fprintf(opt->file, ":%06o %06o %s ", p->one->mode, p->two->mode,
      diff_aligned_abbrev(&p->one->oid, opt->abbrev));
    fprintf(opt->file, "%s ",
      diff_aligned_abbrev(&p->two->oid, opt->abbrev));
  }
  if (p->score) {
    fprintf(opt->file, "%c%03d%c", p->status, similarity_index(p),
      inter_name_termination);
  } else {
    fprintf(opt->file, "%c%c", p->status, inter_name_termination);
  }

  if (p->status == DIFF_STATUS_COPIED ||
      p->status == DIFF_STATUS_RENAMED) {
    const char *name_a, *name_b;
    name_a = p->one->path;
    name_b = p->two->path;
    strip_prefix(opt->prefix_length, &name_a, &name_b);
    write_name_quoted(name_a, opt->file, inter_name_termination);
    write_name_quoted(name_b, opt->file, line_termination);
  } else {
    const char *name_a, *name_b;
    name_a = p->one->mode ? p->one->path : p->two->path;
    name_b = NULL;
    strip_prefix(opt->prefix_length, &name_a, &name_b);
    write_name_quoted(name_a, opt->file, line_termination);
  }
}

int diff_unmodified_pair(struct diff_filepair *p)
{
  /* This function is written stricter than necessary to support
   * the currently implemented transformers, but the idea is to
   * let transformers to produce diff_filepairs any way they want,
   * and filter and clean them up here before producing the output.
   */
  struct diff_filespec *one = p->one, *two = p->two;

  if (DIFF_PAIR_UNMERGED(p))
    return 0; /* unmerged is interesting */

  /* deletion, addition, mode or type change
   * and rename are all interesting.
   */
  if (DIFF_FILE_VALID(one) != DIFF_FILE_VALID(two) ||
      DIFF_PAIR_MODE_CHANGED(p) ||
      strcmp(one->path, two->path))
    return 0;

  /* both are valid and point at the same path.  that is, we are
   * dealing with a change.
   */
  if (one->oid_valid && two->oid_valid &&
      oideq(&one->oid, &two->oid) &&
      !one->dirty_submodule && !two->dirty_submodule)
    return 1; /* no change */
  if (!one->oid_valid && !two->oid_valid)
    return 1; /* both look at the same file on the filesystem. */
  return 0;
}

static void diff_flush_patch(struct diff_filepair *p, struct diff_options *o)
{
  int include_conflict_headers =
      (additional_headers(o, p->one->path) &&
       !o->pickaxe_opts &&
       (!o->filter || filter_bit_tst(DIFF_STATUS_UNMERGED, o)));

  /*
   * Check if we can return early without showing a diff.  Note that
   * diff_filepair only stores {oid, path, mode, is_valid}
   * information for each path, and thus diff_unmodified_pair() only
   * considers those bits of info.  However, we do not want pairs
   * created by create_filepairs_for_header_only_notifications()
   * (which always look like unmodified pairs) to be ignored, so
   * return early if both p is unmodified AND we don't want to
   * include_conflict_headers.
   */
  if (diff_unmodified_pair(p) && !include_conflict_headers)
    return;

  /* Actually, we can also return early to avoid showing tree diffs */
  if ((DIFF_FILE_VALID(p->one) && S_ISDIR(p->one->mode)) ||
      (DIFF_FILE_VALID(p->two) && S_ISDIR(p->two->mode)))
    return;

  run_diff(p, o);
}

/* return 1 if any change is found; otherwise, return 0 */
static int diff_flush_patch_quietly(struct diff_filepair *p, struct diff_options *o)
{
  FILE *saved_file = o->file;
  int saved_found_changes = o->found_changes;
  int ret;

  o->file = NULL;
  o->found_changes = 0;
  diff_flush_patch(p, o);
  ret = o->found_changes;
  o->file = saved_file;
  o->found_changes |= saved_found_changes;
  return ret;
}

static void diff_flush_stat(struct diff_filepair *p, struct diff_options *o,
          struct diffstat_t *diffstat)
{
  if (diff_unmodified_pair(p))
    return;

  if ((DIFF_FILE_VALID(p->one) && S_ISDIR(p->one->mode)) ||
      (DIFF_FILE_VALID(p->two) && S_ISDIR(p->two->mode)))
    return; /* no useful stat for tree diffs */

  run_diffstat(p, o, diffstat);
}

static void diff_flush_checkdiff(struct diff_filepair *p,
    struct diff_options *o)
{
  if (diff_unmodified_pair(p))
    return;

  if ((DIFF_FILE_VALID(p->one) && S_ISDIR(p->one->mode)) ||
      (DIFF_FILE_VALID(p->two) && S_ISDIR(p->two->mode)))
    return; /* nothing to check in tree diffs */

  run_checkdiff(p, o);
}

int diff_queue_is_empty(struct diff_options *o)
{
  struct diff_queue_struct *q = &diff_queued_diff;
  int i;
  int include_conflict_headers =
      (o->additional_path_headers &&
       strmap_get_size(o->additional_path_headers) &&
       !o->pickaxe_opts &&
       (!o->filter || filter_bit_tst(DIFF_STATUS_UNMERGED, o)));

  if (include_conflict_headers)
    return 0;

  for (i = 0; i < q->nr; i++)
    if (!diff_unmodified_pair(q->queue[i]))
      return 0;
  return 1;
}

#if DIFF_DEBUG
void diff_debug_filespec(struct diff_filespec *s, int x, const char *one)
{
  fprintf(stderr, "queue[%d] %s (%s) %s %06o %s\n",
    x, one ? one : "",
    s->path,
    DIFF_FILE_VALID(s) ? "valid" : "invalid",
    s->mode,
    s->oid_valid ? oid_to_hex(&s->oid) : "");
  fprintf(stderr, "queue[%d] %s size %lu\n",
    x, one ? one : "",
    s->size);
}

void diff_debug_filepair(const struct diff_filepair *p, int i)
{
  diff_debug_filespec(p->one, i, "one");
  diff_debug_filespec(p->two, i, "two");
  fprintf(stderr, "score %d, status %c rename_used %d broken %d\n",
    p->score, p->status ? p->status : '?',
    p->one->rename_used, p->broken_pair);
}

void diff_debug_queue(const char *msg, struct diff_queue_struct *q)
{
  int i;
  if (msg)
    fprintf(stderr, "%s\n", msg);
  fprintf(stderr, "q->nr = %d\n", q->nr);
  for (i = 0; i < q->nr; i++) {
    struct diff_filepair *p = q->queue[i];
    diff_debug_filepair(p, i);
  }
}
#endif

static void diff_resolve_rename_copy(void)
{
  int i;
  struct diff_filepair *p;
  struct diff_queue_struct *q = &diff_queued_diff;

  diff_debug_queue("resolve-rename-copy", q);

  for (i = 0; i < q->nr; i++) {
    p = q->queue[i];
    p->status = 0; /* undecided */
    if (DIFF_PAIR_UNMERGED(p))
      p->status = DIFF_STATUS_UNMERGED;
    else if (!DIFF_FILE_VALID(p->one))
      p->status = DIFF_STATUS_ADDED;
    else if (!DIFF_FILE_VALID(p->two))
      p->status = DIFF_STATUS_DELETED;
    else if (DIFF_PAIR_TYPE_CHANGED(p))
      p->status = DIFF_STATUS_TYPE_CHANGED;

    /* from this point on, we are dealing with a pair
     * whose both sides are valid and of the same type, i.e.
     * either in-place edit or rename/copy edit.
     */
    else if (DIFF_PAIR_RENAME(p)) {
      /*
       * A rename might have re-connected a broken
       * pair up, causing the pathnames to be the
       * same again. If so, that's not a rename at
       * all, just a modification..
       *
       * Otherwise, see if this source was used for
       * multiple renames, in which case we decrement
       * the count, and call it a copy.
       */
      if (!strcmp(p->one->path, p->two->path))
        p->status = DIFF_STATUS_MODIFIED;
      else if (--p->one->rename_used > 0)
        p->status = DIFF_STATUS_COPIED;
      else
        p->status = DIFF_STATUS_RENAMED;
    }
    else if (!oideq(&p->one->oid, &p->two->oid) ||
       p->one->mode != p->two->mode ||
       p->one->dirty_submodule ||
       p->two->dirty_submodule ||
       is_null_oid(&p->one->oid))
      p->status = DIFF_STATUS_MODIFIED;
    else {
      /* This is a "no-change" entry and should not
       * happen anymore, but prepare for broken callers.
       */
      error("feeding unmodified %s to diffcore",
            p->one->path);
      p->status = DIFF_STATUS_UNKNOWN;
    }
  }
  diff_debug_queue("resolve-rename-copy done", q);
}

static int check_pair_status(struct diff_filepair *p)
{
  switch (p->status) {
  case DIFF_STATUS_UNKNOWN:
    return 0;
  case 0:
    die("internal error in diff-resolve-rename-copy");
  default:
    return 1;
  }
}

static void flush_one_pair(struct diff_filepair *p, struct diff_options *opt)
{
  int fmt = opt->output_format;

  if (fmt & DIFF_FORMAT_CHECKDIFF)
    diff_flush_checkdiff(p, opt);
  else if (fmt & (DIFF_FORMAT_RAW | DIFF_FORMAT_NAME_STATUS))
    diff_flush_raw(p, opt);
  else if (fmt & DIFF_FORMAT_NAME) {
    const char *name_a, *name_b;
    name_a = p->two->path;
    name_b = NULL;
    strip_prefix(opt->prefix_length, &name_a, &name_b);
    fprintf(opt->file, "%s", diff_line_prefix(opt));
    write_name_quoted(name_a, opt->file, opt->line_termination);
  }

  opt->found_changes = 1;
}

static void show_file_mode_name(struct diff_options *opt, const char *newdelete, struct diff_filespec *fs)
{
  struct strbuf sb = STRBUF_INIT;
  if (fs->mode)
    strbuf_addf(&sb, " %s mode %06o ", newdelete, fs->mode);
  else
    strbuf_addf(&sb, " %s ", newdelete);

  quote_c_style(fs->path, &sb, NULL, 0);
  strbuf_addch(&sb, '\n');
  emit_diff_symbol(opt, DIFF_SYMBOL_SUMMARY,
       sb.buf, sb.len, 0);
  strbuf_release(&sb);
}

static void show_mode_change(struct diff_options *opt, struct diff_filepair *p,
    int show_name)
{
  if (p->one->mode && p->two->mode && p->one->mode != p->two->mode) {
    struct strbuf sb = STRBUF_INIT;
    strbuf_addf(&sb, " mode change %06o => %06o",
          p->one->mode, p->two->mode);
    if (show_name) {
      strbuf_addch(&sb, ' ');
      quote_c_style(p->two->path, &sb, NULL, 0);
    }
    strbuf_addch(&sb, '\n');
    emit_diff_symbol(opt, DIFF_SYMBOL_SUMMARY,
         sb.buf, sb.len, 0);
    strbuf_release(&sb);
  }
}

static void show_rename_copy(struct diff_options *opt, const char *renamecopy,
    struct diff_filepair *p)
{
  struct strbuf sb = STRBUF_INIT;
  struct strbuf names = STRBUF_INIT;

  pprint_rename(&names, p->one->path, p->two->path);
  strbuf_addf(&sb, " %s %s (%d%%)\n",
        renamecopy, names.buf, similarity_index(p));
  strbuf_release(&names);
  emit_diff_symbol(opt, DIFF_SYMBOL_SUMMARY,
         sb.buf, sb.len, 0);
  show_mode_change(opt, p, 0);
  strbuf_release(&sb);
}

static void diff_summary(struct diff_options *opt, struct diff_filepair *p)
{
  switch(p->status) {
  case DIFF_STATUS_DELETED:
    show_file_mode_name(opt, "delete", p->one);
    break;
  case DIFF_STATUS_ADDED:
    show_file_mode_name(opt, "create", p->two);
    break;
  case DIFF_STATUS_COPIED:
    show_rename_copy(opt, "copy", p);
    break;
  case DIFF_STATUS_RENAMED:
    show_rename_copy(opt, "rename", p);
    break;
  default:
    if (p->score) {
      struct strbuf sb = STRBUF_INIT;
      strbuf_addstr(&sb, " rewrite ");
      quote_c_style(p->two->path, &sb, NULL, 0);
      strbuf_addf(&sb, " (%d%%)\n", similarity_index(p));
      emit_diff_symbol(opt, DIFF_SYMBOL_SUMMARY,
           sb.buf, sb.len, 0);
      strbuf_release(&sb);
    }
    show_mode_change(opt, p, !p->score);
    break;
  }
}

struct patch_id_t {
  struct git_hash_ctx *ctx;
  int patchlen;
};

static int remove_space(char *line, int len)
{
  int i;
  char *dst = line;
  unsigned char c;

  for (i = 0; i < len; i++)
    if (!isspace((c = line[i])))
      *dst++ = c;

  return dst - line;
}

void flush_one_hunk(struct object_id *result, struct git_hash_ctx *ctx)
{
  unsigned char hash[GIT_MAX_RAWSZ];
  unsigned short carry = 0;
  int i;

  git_hash_final(hash, ctx);
  git_hash_init(ctx, the_hash_algo);
  /* 20-byte sum, with carry */
  for (i = 0; i < the_hash_algo->rawsz; ++i) {
    carry += result->hash[i] + hash[i];
    result->hash[i] = carry;
    carry >>= 8;
  }
}

static int patch_id_consume(void *priv, char *line, unsigned long len)
{
  struct patch_id_t *data = priv;
  int new_len;

  if (len > 12 && starts_with(line, "\\ "))
    return 0;
  new_len = remove_space(line, len);

  git_hash_update(data->ctx, line, new_len);
  data->patchlen += new_len;
  return 0;
}

static void patch_id_add_string(struct git_hash_ctx *ctx, const char *str)
{
  git_hash_update(ctx, str, strlen(str));
}

static void patch_id_add_mode(struct git_hash_ctx *ctx, unsigned mode)
{
  /* large enough for 2^32 in octal */
  char buf[12];
  int len = xsnprintf(buf, sizeof(buf), "%06o", mode);
  git_hash_update(ctx, buf, len);
}

/* returns 0 upon success, and writes result into oid */
static int diff_get_patch_id(struct diff_options *options, struct object_id *oid, int diff_header_only)
{
  struct diff_queue_struct *q = &diff_queued_diff;
  int i;
  struct git_hash_ctx ctx;
  struct patch_id_t data;

  git_hash_init(&ctx, the_hash_algo);
  memset(&data, 0, sizeof(struct patch_id_t));
  data.ctx = &ctx;
  oidclr(oid, the_repository->hash_algo);

  for (i = 0; i < q->nr; i++) {
    xpparam_t xpp;
    xdemitconf_t xecfg;
    mmfile_t mf1, mf2;
    struct diff_filepair *p = q->queue[i];
    int len1, len2;

    memset(&xpp, 0, sizeof(xpp));
    memset(&xecfg, 0, sizeof(xecfg));
    if (p->status == 0)
      return error("internal diff status error");
    if (p->status == DIFF_STATUS_UNKNOWN)
      continue;
    if (diff_unmodified_pair(p))
      continue;
    if ((DIFF_FILE_VALID(p->one) && S_ISDIR(p->one->mode)) ||
        (DIFF_FILE_VALID(p->two) && S_ISDIR(p->two->mode)))
      continue;
    if (DIFF_PAIR_UNMERGED(p))
      continue;

    diff_fill_oid_info(p->one, options->repo->index);
    diff_fill_oid_info(p->two, options->repo->index);

    len1 = remove_space(p->one->path, strlen(p->one->path));
    len2 = remove_space(p->two->path, strlen(p->two->path));
    patch_id_add_string(&ctx, "diff--git");
    patch_id_add_string(&ctx, "a/");
    git_hash_update(&ctx, p->one->path, len1);
    patch_id_add_string(&ctx, "b/");
    git_hash_update(&ctx, p->two->path, len2);

    if (p->one->mode == 0) {
      patch_id_add_string(&ctx, "newfilemode");
      patch_id_add_mode(&ctx, p->two->mode);
    } else if (p->two->mode == 0) {
      patch_id_add_string(&ctx, "deletedfilemode");
      patch_id_add_mode(&ctx, p->one->mode);
    } else if (p->one->mode != p->two->mode) {
      patch_id_add_string(&ctx, "oldmode");
      patch_id_add_mode(&ctx, p->one->mode);
      patch_id_add_string(&ctx, "newmode");
      patch_id_add_mode(&ctx, p->two->mode);
    }

    if (diff_header_only) {
      /* don't do anything since we're only populating header info */
    } else if (diff_filespec_is_binary(options->repo, p->one) ||
        diff_filespec_is_binary(options->repo, p->two)) {
      git_hash_update(&ctx, oid_to_hex(&p->one->oid),
          the_hash_algo->hexsz);
      git_hash_update(&ctx, oid_to_hex(&p->two->oid),
          the_hash_algo->hexsz);
    } else {
      if (p->one->mode == 0) {
        patch_id_add_string(&ctx, "---/dev/null");
        patch_id_add_string(&ctx, "+++b/");
        git_hash_update(&ctx, p->two->path, len2);
      } else if (p->two->mode == 0) {
        patch_id_add_string(&ctx, "---a/");
        git_hash_update(&ctx, p->one->path, len1);
        patch_id_add_string(&ctx, "+++/dev/null");
      } else {
        patch_id_add_string(&ctx, "---a/");
        git_hash_update(&ctx, p->one->path, len1);
        patch_id_add_string(&ctx, "+++b/");
        git_hash_update(&ctx, p->two->path, len2);
      }

      if (fill_mmfile(options->repo, &mf1, p->one) < 0 ||
          fill_mmfile(options->repo, &mf2, p->two) < 0)
        return error("unable to read files to diff");
      xpp.flags = 0;
      xecfg.ctxlen = 3;
      xecfg.flags = XDL_EMIT_NO_HUNK_HDR;
      if (xdi_diff_outf(&mf1, &mf2, NULL,
            patch_id_consume, &data, &xpp, &xecfg))
        return error("unable to generate patch-id diff for %s",
               p->one->path);
    }
    flush_one_hunk(oid, &ctx);
  }

  git_hash_discard(&ctx);
  return 0;
}

int diff_flush_patch_id(struct diff_options *options, struct object_id *oid, int diff_header_only)
{
  struct diff_queue_struct *q = &diff_queued_diff;
  int result = diff_get_patch_id(options, oid, diff_header_only);

  diff_queue_clear(q);

  return result;
}

static int is_summary_empty(const struct diff_queue_struct *q)
{
  int i;

  for (i = 0; i < q->nr; i++) {
    const struct diff_filepair *p = q->queue[i];

    switch (p->status) {
    case DIFF_STATUS_DELETED:
    case DIFF_STATUS_ADDED:
    case DIFF_STATUS_COPIED:
    case DIFF_STATUS_RENAMED:
      return 0;
    default:
      if (p->score)
        return 0;
      if (p->one->mode && p->two->mode &&
          p->one->mode != p->two->mode)
        return 0;
      break;
    }
  }
  return 1;
}

static const char rename_limit_warning[] =
N_("exhaustive rename detection was skipped due to too many files.");

static const char degrade_cc_to_c_warning[] =
N_("only found copies from modified paths due to too many files.");

static const char rename_limit_advice[] =
N_("you may want to set your %s variable to at least "
   "%d and retry the command.");

void diff_warn_rename_limit(const char *varname, int needed, int degraded_cc)
{
  fflush(stdout);
  if (degraded_cc)
    warning(_(degrade_cc_to_c_warning));
  else if (needed)
    warning(_(rename_limit_warning));
  else
    return;
  if (0 < needed)
    warning(_(rename_limit_advice), varname, needed);
}

static void create_filepairs_for_header_only_notifications(struct diff_options *o)
{
  struct strset present;
  struct diff_queue_struct *q = &diff_queued_diff;
  struct hashmap_iter iter;
  struct strmap_entry *e;
  int i;

  strset_init_with_options(&present, /*pool*/ NULL, /*strdup*/ 0);

  /*
   * Find out which paths exist in diff_queued_diff, preferring
   * one->path for any pair that has multiple paths.
   */
  for (i = 0; i < q->nr; i++) {
    struct diff_filepair *p = q->queue[i];
    char *path = p->one->path ? p->one->path : p->two->path;

    if (strmap_contains(o->additional_path_headers, path))
      strset_add(&present, path);
  }

  /*
   * Loop over paths in additional_path_headers; for each NOT already
   * in diff_queued_diff, create a synthetic filepair and insert that
   * into diff_queued_diff.
   */
  strmap_for_each_entry(o->additional_path_headers, &iter, e) {
    if (!strset_contains(&present, e->key)) {
      struct diff_filespec *one, *two;
      struct diff_filepair *p;

      one = alloc_filespec(e->key);
      two = alloc_filespec(e->key);
      fill_filespec(one, null_oid(the_hash_algo), 0, 0);
      fill_filespec(two, null_oid(the_hash_algo), 0, 0);
      p = diff_queue(q, one, two);
      p->status = DIFF_STATUS_MODIFIED;
    }
  }

  /* Re-sort the filepairs */
  diffcore_fix_diff_index();

  /* Cleanup */
  strset_clear(&present);
}

static void diff_flush_patch_all_file_pairs(struct diff_options *o)
{
  int i;
  static struct emitted_diff_symbols esm = EMITTED_DIFF_SYMBOLS_INIT;
  struct diff_queue_struct *q = &diff_queued_diff;

  if (WSEH_NEW & WS_RULE_MASK)
    BUG("WS rules bit mask overlaps with diff symbol flags");

  if (o->color_moved && want_color(o->use_color))
    o->emitted_symbols = &esm;

  if (o->additional_path_headers)
    create_filepairs_for_header_only_notifications(o);

  for (i = 0; i < q->nr; i++) {
    struct diff_filepair *p = q->queue[i];
    if (check_pair_status(p))
      diff_flush_patch(p, o);
  }

  if (o->emitted_symbols) {
    struct mem_pool entry_pool;
    struct moved_entry_list *entry_list;

    mem_pool_init(&entry_pool, 1024 * 1024);
    entry_list = add_lines_to_move_detection(o, &entry_pool);
    mark_color_as_moved(o, entry_list);
    if (o->color_moved == COLOR_MOVED_ZEBRA_DIM)
      dim_moved_lines(o);

    mem_pool_discard(&entry_pool, 0);
    free(entry_list);

    for (i = 0; i < esm.nr; i++)
      emit_diff_symbol_from_struct(o, &esm.buf[i]);

    for (i = 0; i < esm.nr; i++)
      free((void *)esm.buf[i].line);
    esm.nr = 0;

    o->emitted_symbols = NULL;
  }
}

static void diff_free_file(struct diff_options *options)
{
  if (options->close_file && options->file) {
    fclose(options->file);
    options->file = NULL;
  }
}

static void diff_free_ignore_regex(struct diff_options *options)
{
  int i;

  for (i = 0; i < options->ignore_regex_nr; i++) {
    regfree(options->ignore_regex[i]);
    free(options->ignore_regex[i]);
  }

  FREE_AND_NULL(options->ignore_regex);
  options->ignore_regex_nr = 0;
}

void diff_free(struct diff_options *options)
{
  if (options->no_free)
    return;

  if (options->objfind) {
    oidset_clear(options->objfind);
    FREE_AND_NULL(options->objfind);
  }

  FREE_AND_NULL(options->orderfile);
  for (size_t i = 0; i < options->anchors_nr; i++)
    free(options->anchors[i]);
  FREE_AND_NULL(options->anchors);
  options->anchors_nr = options->anchors_alloc = 0;

  diff_free_file(options);
  diff_free_ignore_regex(options);
  clear_pathspec(&options->pathspec);
}

void diff_flush(struct diff_options *options)
{
  struct diff_queue_struct *q = &diff_queued_diff;
  int i, output_format = options->output_format;
  int separator = 0;
  int dirstat_by_line = 0;

  /*
   * Order: raw, stat, summary, patch
   * or:    name/name-status/checkdiff (other bits clear)
   */
  if (!q->nr && !options->additional_path_headers)
    goto free_queue;

  if (output_format & (DIFF_FORMAT_RAW |
           DIFF_FORMAT_NAME |
           DIFF_FORMAT_NAME_STATUS |
           DIFF_FORMAT_CHECKDIFF)) {
    for (i = 0; i < q->nr; i++) {
      struct diff_filepair *p = q->queue[i];

      if (!check_pair_status(p))
        continue;

      if (options->flags.diff_from_contents &&
          !diff_flush_patch_quietly(p, options))
        continue;

      flush_one_pair(p, options);
    }
    separator++;
  }

  if (output_format & DIFF_FORMAT_DIRSTAT && options->flags.dirstat_by_line)
    dirstat_by_line = 1;

  if (output_format & (DIFF_FORMAT_DIFFSTAT|DIFF_FORMAT_SHORTSTAT|DIFF_FORMAT_NUMSTAT) ||
      dirstat_by_line) {
    struct diffstat_t diffstat;

    compute_diffstat(options, &diffstat, q);
    if (output_format & DIFF_FORMAT_NUMSTAT)
      show_numstat(&diffstat, options);
    if (output_format & DIFF_FORMAT_DIFFSTAT)
      show_stats(&diffstat, options);
    if (output_format & DIFF_FORMAT_SHORTSTAT)
      show_shortstats(&diffstat, options);
    if (output_format & DIFF_FORMAT_DIRSTAT && dirstat_by_line)
      show_dirstat_by_line(&diffstat, options);
    free_diffstat_info(&diffstat);
    separator++;
  }
  if ((output_format & DIFF_FORMAT_DIRSTAT) && !dirstat_by_line)
    show_dirstat(options);

  if (output_format & DIFF_FORMAT_SUMMARY && !is_summary_empty(q)) {
    for (i = 0; i < q->nr; i++) {
      diff_summary(options, q->queue[i]);
    }
    separator++;
  }

  if (output_format & DIFF_FORMAT_PATCH) {
    if (separator) {
      emit_diff_symbol(options, DIFF_SYMBOL_SEPARATOR, NULL, 0, 0);
      if (options->stat_sep)
        /* attach patch instead of inline */
        emit_diff_symbol(options, DIFF_SYMBOL_STAT_SEP,
             NULL, 0, 0);
    }

    diff_flush_patch_all_file_pairs(options);
  }

  if (output_format & DIFF_FORMAT_CALLBACK)
    options->format_callback(q, options, options->format_callback_data);

  if (output_format & DIFF_FORMAT_NO_OUTPUT &&
      options->flags.exit_with_status &&
      options->flags.diff_from_contents) {
    for (i = 0; i < q->nr; i++) {
      struct diff_filepair *p = q->queue[i];
      if (check_pair_status(p))
        diff_flush_patch_quietly(p, options);
      if (options->found_changes)
        break;
    }
  }

free_queue:
  diff_queue_clear(q);
  diff_free(options);

  /*
   * Report the content-level differences with HAS_CHANGES;
   * diff_addremove/diff_change does not set the bit when
   * DIFF_FROM_CONTENTS is in effect (e.g. with -w).
   */
  if (options->flags.diff_from_contents) {
    if (options->found_changes)
      options->flags.has_changes = 1;
    else
      options->flags.has_changes = 0;
  }
}

static int match_filter(const struct diff_options *options, const struct diff_filepair *p)
{
  return (((p->status == DIFF_STATUS_MODIFIED) &&
     ((p->score &&
       filter_bit_tst(DIFF_STATUS_FILTER_BROKEN, options)) ||
      (!p->score &&
       filter_bit_tst(DIFF_STATUS_MODIFIED, options)))) ||
    ((p->status != DIFF_STATUS_MODIFIED) &&
     filter_bit_tst(p->status, options)));
}

static void diffcore_apply_filter(struct diff_options *options)
{
  int i;
  struct diff_queue_struct *q = &diff_queued_diff;
  struct diff_queue_struct outq = DIFF_QUEUE_INIT;

  if (!options->filter)
    return;

  if (filter_bit_tst(DIFF_STATUS_FILTER_AON, options)) {
    int found;
    for (i = found = 0; !found && i < q->nr; i++) {
      if (match_filter(options, q->queue[i]))
        found++;
    }
    if (found)
      return;

    /* otherwise we will clear the whole queue
     * by copying the empty outq at the end of this
     * function, but first clear the current entries
     * in the queue.
     */
    for (i = 0; i < q->nr; i++)
      diff_free_filepair(q->queue[i]);
  }
  else {
    /* Only the matching ones */
    for (i = 0; i < q->nr; i++) {
      struct diff_filepair *p = q->queue[i];
      if (match_filter(options, p))
        diff_q(&outq, p);
      else
        diff_free_filepair(p);
    }
  }
  free(q->queue);
  *q = outq;
}

/* Check whether two filespecs with the same mode and size are identical */
static int diff_filespec_is_identical(struct repository *r,
              struct diff_filespec *one,
              struct diff_filespec *two)
{
  if (S_ISGITLINK(one->mode))
    return 0;
  if (diff_populate_filespec(r, one, NULL))
    return 0;
  if (diff_populate_filespec(r, two, NULL))
    return 0;
  return !memcmp(one->data, two->data, one->size);
}

static int diff_filespec_check_stat_unmatch(struct repository *r,
              struct diff_filepair *p)
{
  struct diff_populate_filespec_options dpf_options = {
    .check_size_only = 1,
    .missing_object_cb = diff_queued_diff_prefetch,
    .missing_object_data = r,
  };

  if (p->done_skip_stat_unmatch)
    return p->skip_stat_unmatch_result;

  p->done_skip_stat_unmatch = 1;
  p->skip_stat_unmatch_result = 0;
  /*
   * 1. Entries that come from stat info dirtiness
   *    always have both sides (iow, not create/delete),
   *    one side of the object name is unknown, with
   *    the same mode and size.  Keep the ones that
   *    do not match these criteria.  They have real
   *    differences.
   *
   * 2. At this point, the file is known to be modified,
   *    with the same mode and size, and the object
   *    name of one side is unknown.  Need to inspect
   *    the identical contents.
   */
  if (!DIFF_FILE_VALID(p->one) || /* (1) */
      !DIFF_FILE_VALID(p->two) ||
      (p->one->oid_valid && p->two->oid_valid) ||
      (p->one->mode != p->two->mode) ||
      diff_populate_filespec(r, p->one, &dpf_options) ||
      diff_populate_filespec(r, p->two, &dpf_options) ||
      (p->one->size != p->two->size) ||
      !diff_filespec_is_identical(r, p->one, p->two)) /* (2) */
    p->skip_stat_unmatch_result = 1;
  return p->skip_stat_unmatch_result;
}

static void diffcore_skip_stat_unmatch(struct diff_options *diffopt)
{
  int i;
  struct diff_queue_struct *q = &diff_queued_diff;
  struct diff_queue_struct outq = DIFF_QUEUE_INIT;

  for (i = 0; i < q->nr; i++) {
    struct diff_filepair *p = q->queue[i];

    if (diff_filespec_check_stat_unmatch(diffopt->repo, p))
      diff_q(&outq, p);
    else {
      /*
       * The caller can subtract 1 from skip_stat_unmatch
       * to determine how many paths were dirty only
       * due to stat info mismatch.
       */
      if (!diffopt->flags.no_index)
        diffopt->skip_stat_unmatch++;
      diff_free_filepair(p);
      q->queue[i] = NULL;
    }
  }
  free(q->queue);
  *q = outq;
}

static int diffnamecmp(const void *a_, const void *b_)
{
  const struct diff_filepair *a = *((const struct diff_filepair **)a_);
  const struct diff_filepair *b = *((const struct diff_filepair **)b_);
  const char *name_a, *name_b;

  name_a = a->one ? a->one->path : a->two->path;
  name_b = b->one ? b->one->path : b->two->path;
  return strcmp(name_a, name_b);
}

void diffcore_fix_diff_index(void)
{
  struct diff_queue_struct *q = &diff_queued_diff;
  QSORT(q->queue, q->nr, diffnamecmp);
}

void diff_add_if_missing(struct repository *r,
       struct oid_array *to_fetch,
       const struct diff_filespec *filespec)
{
  if (filespec && filespec->oid_valid &&
      !S_ISGITLINK(filespec->mode) &&
      odb_read_object_info_extended(r->objects, &filespec->oid, NULL,
            OBJECT_INFO_FOR_PREFETCH))
    oid_array_append(to_fetch, &filespec->oid);
}

void diff_queued_diff_prefetch(void *repository)
{
  struct repository *repo = repository;
  int i;
  struct diff_queue_struct *q = &diff_queued_diff;
  struct oid_array to_fetch = OID_ARRAY_INIT;

  for (i = 0; i < q->nr; i++) {
    struct diff_filepair *p = q->queue[i];

    if (!p)
      continue;

    diff_add_if_missing(repo, &to_fetch, p->one);
    diff_add_if_missing(repo, &to_fetch, p->two);
  }

  /*
   * NEEDSWORK: Consider deduplicating the OIDs sent.
   */
  promisor_remote_get_direct(repo, to_fetch.oid, to_fetch.nr);

  oid_array_clear(&to_fetch);
}

void init_diffstat_widths(struct diff_options *options)
{
  options->stat_width = -1;        /* use full terminal width */
  options->stat_name_width = -1;   /* respect diff.statNameWidth config */
  options->stat_graph_width = -1;  /* respect diff.statGraphWidth config */
}

void diffcore_std(struct diff_options *options)
{
  int output_formats_to_prefetch = DIFF_FORMAT_DIFFSTAT |
    DIFF_FORMAT_NUMSTAT |
    DIFF_FORMAT_PATCH |
    DIFF_FORMAT_SHORTSTAT |
    DIFF_FORMAT_DIRSTAT;

  /*
   * Check if the user requested a blob-data-requiring diff output and/or
   * break-rewrite detection (which requires blob data). If yes, prefetch
   * the diff pairs.
   *
   * If no prefetching occurs, diffcore_rename() will prefetch if it
   * decides that it needs inexact rename detection.
   */
  if (repo_has_promisor_remote(options->repo) &&
      (options->output_format & output_formats_to_prefetch ||
       options->pickaxe_opts & DIFF_PICKAXE_KINDS_MASK))
    diff_queued_diff_prefetch(options->repo);

  /* NOTE please keep the following in sync with diff_tree_combined() */
  if (options->skip_stat_unmatch)
    diffcore_skip_stat_unmatch(options);
  if (!options->found_follow) {
    /* See try_to_follow_renames() in tree-diff.c */
    if (options->break_opt != -1)
      diffcore_break(options->repo,
               options->break_opt);
    if (options->detect_rename)
      diffcore_rename(options);
    if (options->break_opt != -1)
      diffcore_merge_broken();
  }
  if (options->pickaxe_opts & DIFF_PICKAXE_KINDS_MASK)
    diffcore_pickaxe(options);
  if (options->orderfile)
    diffcore_order(options->orderfile);
  if (options->rotate_to)
    diffcore_rotate(options);
  if (!options->found_follow && !options->skip_resolving_statuses)
    /* See try_to_follow_renames() in tree-diff.c */
    diff_resolve_rename_copy();
  diffcore_apply_filter(options);

  if (diff_queued_diff.nr && !options->flags.diff_from_contents)
    options->flags.has_changes = 1;
  else
    options->flags.has_changes = 0;

  options->found_follow = 0;
}

int diff_result_code(struct rev_info *revs)
{
  struct diff_options *opt = &revs->diffopt;
  int result = 0;

  if (revs->remerge_diff) {
    tmp_objdir_destroy(revs->remerge_objdir);
    revs->remerge_objdir = NULL;
  }

  diff_warn_rename_limit("diff.renameLimit",
             opt->needed_rename_limit,
             opt->degraded_cc_to_c);

  if (opt->flags.exit_with_status &&
      opt->flags.has_changes)
    result |= 01;
  if ((opt->output_format & DIFF_FORMAT_CHECKDIFF) &&
      opt->flags.check_failed)
    result |= 02;
  return result;
}

int diff_can_quit_early(struct diff_options *opt)
{
  return (opt->flags.quick &&
    !opt->filter &&
    opt->flags.has_changes);
}

/*
 * Shall changes to this submodule be ignored?
 *
 * Submodule changes can be configured to be ignored separately for each path,
 * but that configuration can be overridden from the command line.
 */
static int is_submodule_ignored(const char *path, struct diff_options *options)
{
  int ignored = 0;
  struct diff_flags orig_flags = options->flags;
  if (!options->flags.override_submodule_config)
    set_diffopt_flags_from_submodule_config(options, path);
  if (options->flags.ignore_submodules)
    ignored = 1;
  options->flags = orig_flags;
  return ignored;
}

void compute_diffstat(struct diff_options *options,
          struct diffstat_t *diffstat,
          struct diff_queue_struct *q)
{
  int i;

  memset(diffstat, 0, sizeof(struct diffstat_t));
  for (i = 0; i < q->nr; i++) {
    struct diff_filepair *p = q->queue[i];
    if (check_pair_status(p))
      diff_flush_stat(p, options, diffstat);
  }
  options->found_changes = !!diffstat->nr;
}

struct diff_filepair *diff_queue_addremove(struct diff_queue_struct *queue,
             struct diff_options *options,
             int addremove, unsigned mode,
             const struct object_id *oid,
             int oid_valid,
             const char *concatpath,
             unsigned dirty_submodule)
{
  struct diff_filespec *one, *two;
  struct diff_filepair *pair;

  if (S_ISGITLINK(mode) && is_submodule_ignored(concatpath, options))
    return NULL;

  /* This may look odd, but it is a preparation for
   * feeding "there are unchanged files which should
   * not produce diffs, but when you are doing copy
   * detection you would need them, so here they are"
   * entries to the diff-core.  They will be prefixed
   * with something like '=' or '*' (I haven't decided
   * which but should not make any difference).
   * Feeding the same new and old to diff_change()
   * also has the same effect.
   * Before the final output happens, they are pruned after
   * merged into rename/copy pairs as appropriate.
   */
  if (options->flags.reverse_diff)
    addremove = (addremove == '+' ? '-' :
           addremove == '-' ? '+' : addremove);

  if (options->prefix &&
      strncmp(concatpath, options->prefix, options->prefix_length))
    return NULL;

  one = alloc_filespec(concatpath);
  two = alloc_filespec(concatpath);

  if (addremove != '+')
    fill_filespec(one, oid, oid_valid, mode);
  if (addremove != '-') {
    fill_filespec(two, oid, oid_valid, mode);
    two->dirty_submodule = dirty_submodule;
  }

  pair = diff_queue(queue, one, two);
  if (!options->flags.diff_from_contents)
    options->flags.has_changes = 1;

  return pair;
}

struct diff_filepair *diff_queue_change(struct diff_queue_struct *queue,
          struct diff_options *options,
          unsigned old_mode, unsigned new_mode,
          const struct object_id *old_oid,
          const struct object_id *new_oid,
          int old_oid_valid, int new_oid_valid,
          const char *concatpath,
          unsigned old_dirty_submodule,
          unsigned new_dirty_submodule)
{
  struct diff_filespec *one, *two;
  struct diff_filepair *p;

  if (S_ISGITLINK(old_mode) && S_ISGITLINK(new_mode) &&
      is_submodule_ignored(concatpath, options))
    return NULL;

  if (options->flags.reverse_diff) {
    SWAP(old_mode, new_mode);
    SWAP(old_oid, new_oid);
    SWAP(old_oid_valid, new_oid_valid);
    SWAP(old_dirty_submodule, new_dirty_submodule);
  }

  if (options->prefix &&
      strncmp(concatpath, options->prefix, options->prefix_length))
    return NULL;

  one = alloc_filespec(concatpath);
  two = alloc_filespec(concatpath);
  fill_filespec(one, old_oid, old_oid_valid, old_mode);
  fill_filespec(two, new_oid, new_oid_valid, new_mode);
  one->dirty_submodule = old_dirty_submodule;
  two->dirty_submodule = new_dirty_submodule;
  p = diff_queue(queue, one, two);

  if (options->flags.diff_from_contents)
    return p;

  if (options->flags.quick && options->skip_stat_unmatch &&
      !diff_filespec_check_stat_unmatch(options->repo, p)) {
    diff_free_filespec_data(p->one);
    diff_free_filespec_data(p->two);
    return p;
  }

  options->flags.has_changes = 1;

  return p;
}

void diff_addremove(struct diff_options *options, int addremove, unsigned mode,
        const struct object_id *oid, int oid_valid,
        const char *concatpath, unsigned dirty_submodule)
{
  diff_queue_addremove(&diff_queued_diff, options, addremove, mode, oid,
           oid_valid, concatpath, dirty_submodule);
}

void diff_change(struct diff_options *options,
     unsigned old_mode, unsigned new_mode,
     const struct object_id *old_oid,
     const struct object_id *new_oid,
     int old_oid_valid, int new_oid_valid,
     const char *concatpath,
     unsigned old_dirty_submodule, unsigned new_dirty_submodule)
{
  diff_queue_change(&diff_queued_diff, options, old_mode, new_mode,
        old_oid, new_oid, old_oid_valid, new_oid_valid,
        concatpath, old_dirty_submodule, new_dirty_submodule);
}

void diff_same(struct diff_options *options,
         unsigned mode,
         const struct object_id *oid,
         const char *concatpath)
{
  struct diff_filespec *one;

  if (S_ISGITLINK(mode) && is_submodule_ignored(concatpath, options))
    return;

  if (options->prefix &&
      strncmp(concatpath, options->prefix, options->prefix_length))
    return;

  one = alloc_filespec(concatpath);
  fill_filespec(one, oid, 1, mode);
  one->count++;
  diff_queue(&diff_queued_diff, one, one);
}

struct diff_filepair *diff_unmerge(struct diff_options *options, const char *path)
{
  struct diff_filepair *pair;
  struct diff_filespec *one, *two;

  if (options->prefix &&
      strncmp(path, options->prefix, options->prefix_length))
    return NULL;

  one = alloc_filespec(path);
  two = alloc_filespec(path);
  pair = diff_queue(&diff_queued_diff, one, two);
  pair->is_unmerged = 1;
  return pair;
}

static char *run_textconv(struct repository *r,
        const char *pgm,
        struct diff_filespec *spec,
        size_t *outsize)
{
  struct diff_tempfile *temp;
  struct child_process child = CHILD_PROCESS_INIT;
  struct strbuf buf = STRBUF_INIT;
  int err = 0;

  temp = prepare_temp_file(r, spec);
  strvec_push(&child.args, pgm);
  strvec_push(&child.args, temp->name);

  child.use_shell = 1;
  child.out = -1;
  if (start_command(&child)) {
    remove_tempfile();
    return NULL;
  }

  if (strbuf_read(&buf, child.out, 0) < 0)
    err = error("error reading from textconv command '%s'", pgm);
  close(child.out);

  if (finish_command(&child) || err) {
    strbuf_release(&buf);
    remove_tempfile();
    return NULL;
  }
  remove_tempfile();

  return strbuf_detach(&buf, outsize);
}

size_t fill_textconv(struct repository *r,
         struct userdiff_driver *driver,
         struct diff_filespec *df,
         char **outbuf)
{
  size_t size;

  if (!driver) {
    if (!DIFF_FILE_VALID(df)) {
      *outbuf = (char *) "";
      return 0;
    }
    if (diff_populate_filespec(r, df, NULL))
      die("unable to read files to diff");
    *outbuf = df->data;
    return df->size;
  }

  if (!driver->textconv)
    BUG("fill_textconv called with non-textconv driver");

  if (driver->textconv_cache && df->oid_valid) {
    *outbuf = notes_cache_get(driver->textconv_cache,
            &df->oid,
            &size);
    if (*outbuf)
      return size;
  }

  *outbuf = run_textconv(r, driver->textconv, df, &size);
  if (!*outbuf)
    die("unable to read files to diff");

  if (driver->textconv_cache && df->oid_valid) {
    /* ignore errors, as we might be in a readonly repository */
    notes_cache_put(driver->textconv_cache, &df->oid, *outbuf,
        size);
    /*
     * we could save up changes and flush them all at the end,
     * but we would need an extra call after all diffing is done.
     * Since generating a cache entry is the slow path anyway,
     * this extra overhead probably isn't a big deal.
     */
    notes_cache_write(driver->textconv_cache);
  }

  return size;
}

int textconv_object(struct repository *r,
        const char *path,
        unsigned mode,
        const struct object_id *oid,
        int oid_valid,
        char **buf,
        unsigned long *buf_size)
{
  struct diff_filespec *df;
  struct userdiff_driver *textconv;

  df = alloc_filespec(path);
  fill_filespec(df, oid, oid_valid, mode);
  textconv = get_textconv(r, df);
  if (!textconv) {
    free_filespec(df);
    return 0;
  }

  *buf_size = fill_textconv(r, textconv, df, buf);
  free_filespec(df);
  return 1;
}

void setup_diff_pager(struct diff_options *opt)
{
  /*
   * If the user asked for our exit code, then either they want --quiet
   * or --exit-code. We should definitely not bother with a pager in the
   * former case, as we will generate no output. Since we still properly
   * report our exit code even when a pager is run, we _could_ run a
   * pager with --exit-code. But since we have not done so historically,
   * and because it is easy to find people oneline advising "git diff
   * --exit-code" in hooks and other scripts, we do not do so.
   */
  if (!opt->flags.exit_with_status &&
      check_pager_config(the_repository, "diff") != 0)
    setup_pager(the_repository);
}

Coverage Report

Created: 2026-10-17 07:15