/src/git/rerere.c

Source
#define USE_THE_REPOSITORY_VARIABLE
#define DISABLE_SIGN_COMPARE_WARNINGS

#include "git-compat-util.h"
#include "abspath.h"
#include "config.h"
#include "copy.h"
#include "environment.h"
#include "gettext.h"
#include "hex.h"
#include "lockfile.h"
#include "string-list.h"
#include "read-cache-ll.h"
#include "rerere.h"
#include "xdiff-interface.h"
#include "dir.h"
#include "resolve-undo.h"
#include "merge-ll.h"
#include "path.h"
#include "pathspec.h"
#include "object-file.h"
#include "odb.h"
#include "strmap.h"

#define RESOLVED 0
#define PUNTED 1
#define THREE_STAGED 2
void *RERERE_RESOLVED = &RERERE_RESOLVED;

/* if rerere_enabled == -1, fall back to detection of .git/rr-cache */
static int rerere_enabled = -1;

/* automatically update cleanly resolved paths to the index */
static int rerere_autoupdate;

#define RR_HAS_POSTIMAGE 1
#define RR_HAS_PREIMAGE 2
struct rerere_dir {
  int status_alloc, status_nr;
  unsigned char *status;
  char name[FLEX_ARRAY];
};

static struct strmap rerere_dirs = STRMAP_INIT;

static void free_rerere_dirs(void)
{
  struct hashmap_iter iter;
  struct strmap_entry *ent;

  strmap_for_each_entry(&rerere_dirs, &iter, ent) {
    struct rerere_dir *rr_dir = ent->value;
    free(rr_dir->status);
    free(rr_dir);
  }
  strmap_clear(&rerere_dirs, 0);
}

static void free_rerere_id(struct string_list_item *item)
{
  free(item->util);
}

static const char *rerere_id_hex(const struct rerere_id *id)
{
  return id->collection->name;
}

static void fit_variant(struct rerere_dir *rr_dir, int variant)
{
  variant++;
  ALLOC_GROW(rr_dir->status, variant, rr_dir->status_alloc);
  if (rr_dir->status_nr < variant) {
    memset(rr_dir->status + rr_dir->status_nr,
           '\0', variant - rr_dir->status_nr);
    rr_dir->status_nr = variant;
  }
}

static void assign_variant(struct rerere_id *id)
{
  int variant;
  struct rerere_dir *rr_dir = id->collection;

  variant = id->variant;
  if (variant < 0) {
    for (variant = 0; variant < rr_dir->status_nr; variant++)
      if (!rr_dir->status[variant])
        break;
  }
  fit_variant(rr_dir, variant);
  id->variant = variant;
}

const char *rerere_path(struct strbuf *buf, const struct rerere_id *id, const char *file)
{
  if (!file)
    return repo_git_path_replace(the_repository, buf, "rr-cache/%s",
               rerere_id_hex(id));

  if (id->variant <= 0)
    return repo_git_path_replace(the_repository, buf, "rr-cache/%s/%s",
               rerere_id_hex(id), file);

  return repo_git_path_replace(the_repository, buf, "rr-cache/%s/%s.%d",
             rerere_id_hex(id), file, id->variant);
}

static int is_rr_file(const char *name, const char *filename, int *variant)
{
  const char *suffix;
  char *ep;

  if (!strcmp(name, filename)) {
    *variant = 0;
    return 1;
  }
  if (!skip_prefix(name, filename, &suffix) || *suffix != '.')
    return 0;

  errno = 0;
  *variant = strtol(suffix + 1, &ep, 10);
  if (errno || *ep)
    return 0;
  return 1;
}

static void scan_rerere_dir(struct rerere_dir *rr_dir)
{
  struct dirent *de;
  char *path;
  DIR *dir;

  path = repo_git_path(the_repository, "rr-cache/%s", rr_dir->name);
  dir = opendir(path);
  free(path);
  if (!dir)
    return;
  while ((de = readdir(dir)) != NULL) {
    int variant;

    if (is_rr_file(de->d_name, "postimage", &variant)) {
      fit_variant(rr_dir, variant);
      rr_dir->status[variant] |= RR_HAS_POSTIMAGE;
    } else if (is_rr_file(de->d_name, "preimage", &variant)) {
      fit_variant(rr_dir, variant);
      rr_dir->status[variant] |= RR_HAS_PREIMAGE;
    }
  }
  closedir(dir);
}

static struct rerere_dir *find_rerere_dir(const char *hex)
{
  struct rerere_dir *rr_dir;

  rr_dir = strmap_get(&rerere_dirs, hex);
  if (!rr_dir) {
    FLEX_ALLOC_STR(rr_dir, name, hex);
    rr_dir->status = NULL;
    rr_dir->status_nr = 0;
    rr_dir->status_alloc = 0;
    strmap_put(&rerere_dirs, hex, rr_dir);

    scan_rerere_dir(rr_dir);
  }
  return rr_dir;
}

static int has_rerere_resolution(const struct rerere_id *id)
{
  const int both = RR_HAS_POSTIMAGE|RR_HAS_PREIMAGE;
  int variant = id->variant;

  if (variant < 0)
    return 0;
  return ((id->collection->status[variant] & both) == both);
}

static struct rerere_id *new_rerere_id_hex(char *hex)
{
  struct rerere_id *id = xmalloc(sizeof(*id));
  id->collection = find_rerere_dir(hex);
  id->variant = -1; /* not known yet */
  return id;
}

static struct rerere_id *new_rerere_id(unsigned char *hash)
{
  return new_rerere_id_hex(hash_to_hex(hash));
}

/*
 * $GIT_DIR/MERGE_RR file is a collection of records, each of which is
 * "conflict ID", a HT and pathname, terminated with a NUL, and is
 * used to keep track of the set of paths that "rerere" may need to
 * work on (i.e. what is left by the previous invocation of "git
 * rerere" during the current conflict resolution session).
 */
static void read_rr(struct repository *r, struct string_list *rr)
{
  struct strbuf buf = STRBUF_INIT;
  FILE *in = fopen_or_warn(git_path_merge_rr(r), "r");

  if (!in)
    return;
  while (!strbuf_getwholeline(&buf, in, '\0')) {
    char *path;
    unsigned char hash[GIT_MAX_RAWSZ];
    struct rerere_id *id;
    int variant;
    const unsigned hexsz = the_hash_algo->hexsz;

    /* There has to be the hash, tab, path and then NUL */
    if (buf.len < hexsz + 2 || get_hash_hex(buf.buf, hash))
      die(_("corrupt MERGE_RR"));

    if (buf.buf[hexsz] != '.') {
      variant = 0;
      path = buf.buf + hexsz;
    } else {
      errno = 0;
      variant = strtol(buf.buf + hexsz + 1, &path, 10);
      if (errno)
        die(_("corrupt MERGE_RR"));
    }
    if (*(path++) != '\t')
      die(_("corrupt MERGE_RR"));
    buf.buf[hexsz] = '\0';
    id = new_rerere_id_hex(buf.buf);
    id->variant = variant;
    /*
     * make sure id->collection->status has enough space
     * for the variant we are interested in
     */
    fit_variant(id->collection, variant);
    string_list_insert(rr, path)->util = id;
  }
  strbuf_release(&buf);
  fclose(in);
}

static struct lock_file write_lock;

static int write_rr(struct string_list *rr, int out_fd)
{
  int i;
  for (i = 0; i < rr->nr; i++) {
    struct strbuf buf = STRBUF_INIT;
    struct rerere_id *id;

    assert(rr->items[i].util != RERERE_RESOLVED);

    id = rr->items[i].util;
    if (!id)
      continue;
    assert(id->variant >= 0);
    if (0 < id->variant)
      strbuf_addf(&buf, "%s.%d\t%s%c",
            rerere_id_hex(id), id->variant,
            rr->items[i].string, 0);
    else
      strbuf_addf(&buf, "%s\t%s%c",
            rerere_id_hex(id),
            rr->items[i].string, 0);

    if (write_in_full(out_fd, buf.buf, buf.len) < 0)
      die(_("unable to write rerere record"));

    strbuf_release(&buf);
  }
  if (commit_lock_file(&write_lock) != 0)
    die(_("unable to write rerere record"));
  return 0;
}

/*
 * "rerere" interacts with conflicted file contents using this I/O
 * abstraction.  It reads a conflicted contents from one place via
 * "getline()" method, and optionally can write it out after
 * normalizing the conflicted hunks to the "output".  Subclasses of
 * rerere_io embed this structure at the beginning of their own
 * rerere_io object.
 */
struct rerere_io {
  int (*getline)(struct strbuf *, struct rerere_io *);
  FILE *output;
  int wrerror;
  /* some more stuff */
};

static void ferr_write(const void *p, size_t count, FILE *fp, int *err)
{
  if (!count || *err)
    return;
  if (fwrite(p, count, 1, fp) != 1)
    *err = errno;
}

static inline void ferr_puts(const char *s, FILE *fp, int *err)
{
  ferr_write(s, strlen(s), fp, err);
}

static void rerere_io_putstr(const char *str, struct rerere_io *io)
{
  if (io->output)
    ferr_puts(str, io->output, &io->wrerror);
}

static void rerere_io_putmem(const char *mem, size_t sz, struct rerere_io *io)
{
  if (io->output)
    ferr_write(mem, sz, io->output, &io->wrerror);
}

/*
 * Subclass of rerere_io that reads from an on-disk file
 */
struct rerere_io_file {
  struct rerere_io io;
  FILE *input;
};

/*
 * ... and its getline() method implementation
 */
static int rerere_file_getline(struct strbuf *sb, struct rerere_io *io_)
{
  struct rerere_io_file *io = (struct rerere_io_file *)io_;
  return strbuf_getwholeline(sb, io->input, '\n');
}

/*
 * Require the exact number of conflict marker letters, no more, no
 * less, followed by SP or any whitespace
 * (including LF).
 */
static int is_cmarker(char *buf, int marker_char, int marker_size)
{
  int want_sp;

  /*
   * The beginning of our version and the end of their version
   * always are labeled like "<<<<< ours" or ">>>>> theirs",
   * hence we set want_sp for them.  Note that the version from
   * the common ancestor in diff3-style output is not always
   * labelled (e.g. "||||| common" is often seen but "|||||"
   * alone is also valid), so we do not set want_sp.
   */
  want_sp = (marker_char == '<') || (marker_char == '>');

  while (marker_size--)
    if (*buf++ != marker_char)
      return 0;
  if (want_sp && *buf != ' ')
    return 0;
  return isspace(*buf);
}

static void rerere_strbuf_putconflict(struct strbuf *buf, int ch, size_t size)
{
  strbuf_addchars(buf, ch, size);
  strbuf_addch(buf, '\n');
}

static int handle_conflict(struct strbuf *out, struct rerere_io *io,
         int marker_size, struct git_hash_ctx *ctx)
{
  enum {
    RR_SIDE_1 = 0, RR_SIDE_2, RR_ORIGINAL
  } hunk = RR_SIDE_1;
  struct strbuf one = STRBUF_INIT, two = STRBUF_INIT;
  struct strbuf buf = STRBUF_INIT, conflict = STRBUF_INIT;
  int has_conflicts = -1;

  while (!io->getline(&buf, io)) {
    if (is_cmarker(buf.buf, '<', marker_size)) {
      if (handle_conflict(&conflict, io, marker_size, NULL) < 0)
        break;
      if (hunk == RR_SIDE_1)
        strbuf_addbuf(&one, &conflict);
      else
        strbuf_addbuf(&two, &conflict);
      strbuf_release(&conflict);
    } else if (is_cmarker(buf.buf, '|', marker_size)) {
      if (hunk != RR_SIDE_1)
        break;
      hunk = RR_ORIGINAL;
    } else if (is_cmarker(buf.buf, '=', marker_size)) {
      if (hunk != RR_SIDE_1 && hunk != RR_ORIGINAL)
        break;
      hunk = RR_SIDE_2;
    } else if (is_cmarker(buf.buf, '>', marker_size)) {
      if (hunk != RR_SIDE_2)
        break;
      if (strbuf_cmp(&one, &two) > 0)
        strbuf_swap(&one, &two);
      has_conflicts = 1;
      rerere_strbuf_putconflict(out, '<', marker_size);
      strbuf_addbuf(out, &one);
      rerere_strbuf_putconflict(out, '=', marker_size);
      strbuf_addbuf(out, &two);
      rerere_strbuf_putconflict(out, '>', marker_size);
      if (ctx) {
        git_hash_update(ctx, one.buf ?
            one.buf : "",
            one.len + 1);
        git_hash_update(ctx, two.buf ?
            two.buf : "",
            two.len + 1);
      }
      break;
    } else if (hunk == RR_SIDE_1)
      strbuf_addbuf(&one, &buf);
    else if (hunk == RR_ORIGINAL)
      ; /* discard */
    else if (hunk == RR_SIDE_2)
      strbuf_addbuf(&two, &buf);
  }
  strbuf_release(&one);
  strbuf_release(&two);
  strbuf_release(&buf);

  return has_conflicts;
}

/*
 * Read contents a file with conflicts, normalize the conflicts
 * by (1) discarding the common ancestor version in diff3-style,
 * (2) reordering our side and their side so that whichever sorts
 * alphabetically earlier comes before the other one, while
 * computing the "conflict ID", which is just an SHA-1 hash of
 * one side of the conflict, NUL, the other side of the conflict,
 * and NUL concatenated together.
 *
 * Return 1 if conflict hunks are found, 0 if there are no conflict
 * hunks and -1 if an error occurred.
 */
static int handle_path(unsigned char *hash, struct rerere_io *io, int marker_size)
{
  struct git_hash_ctx ctx;
  struct strbuf buf = STRBUF_INIT, out = STRBUF_INIT;
  int has_conflicts = 0;
  if (hash)
    the_hash_algo->init_fn(&ctx);

  while (!io->getline(&buf, io)) {
    if (is_cmarker(buf.buf, '<', marker_size)) {
      has_conflicts = handle_conflict(&out, io, marker_size,
              hash ? &ctx : NULL);
      if (has_conflicts < 0)
        break;
      rerere_io_putmem(out.buf, out.len, io);
      strbuf_reset(&out);
    } else
      rerere_io_putstr(buf.buf, io);
  }
  strbuf_release(&buf);
  strbuf_release(&out);

  if (hash)
    git_hash_final(hash, &ctx);

  return has_conflicts;
}

/*
 * Scan the path for conflicts, do the "handle_path()" thing above, and
 * return the number of conflict hunks found.
 */
static int handle_file(struct index_state *istate,
           const char *path, unsigned char *hash, const char *output)
{
  int has_conflicts = 0;
  struct rerere_io_file io;
  int marker_size = ll_merge_marker_size(istate, path);

  memset(&io, 0, sizeof(io));
  io.io.getline = rerere_file_getline;
  io.input = fopen(path, "r");
  io.io.wrerror = 0;
  if (!io.input)
    return error_errno(_("could not open '%s'"), path);

  if (output) {
    io.io.output = fopen(output, "w");
    if (!io.io.output) {
      error_errno(_("could not write '%s'"), output);
      fclose(io.input);
      return -1;
    }
  }

  has_conflicts = handle_path(hash, (struct rerere_io *)&io, marker_size);

  fclose(io.input);
  if (io.io.wrerror)
    error(_("there were errors while writing '%s' (%s)"),
          path, strerror(io.io.wrerror));
  if (io.io.output && fclose(io.io.output))
    io.io.wrerror = error_errno(_("failed to flush '%s'"), path);

  if (has_conflicts < 0) {
    if (output)
      unlink_or_warn(output);
    return error(_("could not parse conflict hunks in '%s'"), path);
  }
  if (io.io.wrerror)
    return -1;
  return has_conflicts;
}

/*
 * Look at a cache entry at "i" and see if it is not conflicting,
 * conflicting and we are willing to handle, or conflicting and
 * we are unable to handle, and return the determination in *type.
 * Return the cache index to be looked at next, by skipping the
 * stages we have already looked at in this invocation of this
 * function.
 */
static int check_one_conflict(struct index_state *istate, int i, int *type)
{
  const struct cache_entry *e = istate->cache[i];

  if (!ce_stage(e)) {
    *type = RESOLVED;
    return i + 1;
  }

  *type = PUNTED;
  while (i < istate->cache_nr && ce_stage(istate->cache[i]) == 1)
    i++;

  /* Only handle regular files with both stages #2 and #3 */
  if (i + 1 < istate->cache_nr) {
    const struct cache_entry *e2 = istate->cache[i];
    const struct cache_entry *e3 = istate->cache[i + 1];
    if (ce_stage(e2) == 2 &&
        ce_stage(e3) == 3 &&
        ce_same_name(e, e3) &&
        S_ISREG(e2->ce_mode) &&
        S_ISREG(e3->ce_mode))
      *type = THREE_STAGED;
  }

  /* Skip the entries with the same name */
  while (i < istate->cache_nr && ce_same_name(e, istate->cache[i]))
    i++;
  return i;
}

/*
 * Scan the index and find paths that have conflicts that rerere can
 * handle, i.e. the ones that has both stages #2 and #3.
 *
 * NEEDSWORK: we do not record or replay a previous "resolve by
 * deletion" for a delete-modify conflict, as that is inherently risky
 * without knowing what modification is being discarded.  The only
 * safe case, i.e. both side doing the deletion and modification that
 * are identical to the previous round, might want to be handled,
 * though.
 */
static int find_conflict(struct repository *r, struct string_list *conflict)
{
  int i;

  if (repo_read_index(r) < 0)
    return error(_("index file corrupt"));

  for (i = 0; i < r->index->cache_nr;) {
    int conflict_type;
    const struct cache_entry *e = r->index->cache[i];
    i = check_one_conflict(r->index, i, &conflict_type);
    if (conflict_type == THREE_STAGED)
      string_list_insert(conflict, (const char *)e->name);
  }
  return 0;
}

/*
 * The merge_rr list is meant to hold outstanding conflicted paths
 * that rerere could handle.  Abuse the list by adding other types of
 * entries to allow the caller to show "rerere remaining".
 *
 * - Conflicted paths that rerere does not handle are added
 * - Conflicted paths that have been resolved are marked as such
 *   by storing RERERE_RESOLVED to .util field (where conflict ID
 *   is expected to be stored).
 *
 * Do *not* write MERGE_RR file out after calling this function.
 *
 * NEEDSWORK: we may want to fix the caller that implements "rerere
 * remaining" to do this without abusing merge_rr.
 */
int rerere_remaining(struct repository *r, struct string_list *merge_rr)
{
  int i;

  if (setup_rerere(r, merge_rr, RERERE_READONLY))
    return 0;
  if (repo_read_index(r) < 0)
    return error(_("index file corrupt"));

  for (i = 0; i < r->index->cache_nr;) {
    int conflict_type;
    const struct cache_entry *e = r->index->cache[i];
    i = check_one_conflict(r->index, i, &conflict_type);
    if (conflict_type == PUNTED)
      string_list_insert(merge_rr, (const char *)e->name);
    else if (conflict_type == RESOLVED) {
      struct string_list_item *it;
      it = string_list_lookup(merge_rr, (const char *)e->name);
      if (it) {
        free_rerere_id(it);
        it->util = RERERE_RESOLVED;
      }
    }
  }
  return 0;
}

/*
 * Try using the given conflict resolution "ID" to see
 * if that recorded conflict resolves cleanly what we
 * got in the "cur".
 */
static int try_merge(struct index_state *istate,
         const struct rerere_id *id, const char *path,
         mmfile_t *cur, mmbuffer_t *result)
{
  enum ll_merge_result ret;
  mmfile_t base = {NULL, 0}, other = {NULL, 0};
  struct strbuf buf = STRBUF_INIT;

  if (read_mmfile(&base, rerere_path(&buf, id, "preimage")) ||
      read_mmfile(&other, rerere_path(&buf, id, "postimage"))) {
    ret = LL_MERGE_CONFLICT;
  } else {
    /*
     * A three-way merge. Note that this honors user-customizable
     * low-level merge driver settings.
     */
    ret = ll_merge(result, path, &base, NULL, cur, "", &other, "",
             istate, NULL);
  }

  strbuf_release(&buf);
  free(base.ptr);
  free(other.ptr);

  return ret;
}

/*
 * Find the conflict identified by "id"; the change between its
 * "preimage" (i.e. a previous contents with conflict markers) and its
 * "postimage" (i.e. the corresponding contents with conflicts
 * resolved) may apply cleanly to the contents stored in "path", i.e.
 * the conflict this time around.
 *
 * Returns 0 for successful replay of recorded resolution, or non-zero
 * for failure.
 */
static int merge(struct index_state *istate, const struct rerere_id *id, const char *path)
{
  FILE *f;
  int ret;
  struct strbuf buf = STRBUF_INIT;
  mmfile_t cur = {NULL, 0};
  mmbuffer_t result = {NULL, 0};

  /*
   * Normalize the conflicts in path and write it out to
   * "thisimage" temporary file.
   */
  if ((handle_file(istate, path, NULL, rerere_path(&buf, id, "thisimage")) < 0) ||
      read_mmfile(&cur, rerere_path(&buf, id, "thisimage"))) {
    ret = 1;
    goto out;
  }

  ret = try_merge(istate, id, path, &cur, &result);
  if (ret)
    goto out;

  /*
   * A successful replay of recorded resolution.
   * Mark that "postimage" was used to help gc.
   */
  if (utime(rerere_path(&buf, id, "postimage"), NULL) < 0)
    warning_errno(_("failed utime() on '%s'"),
            rerere_path(&buf, id, "postimage"));

  /* Update "path" with the resolution */
  f = fopen(path, "w");
  if (!f)
    return error_errno(_("could not open '%s'"), path);
  if (fwrite(result.ptr, result.size, 1, f) != 1)
    error_errno(_("could not write '%s'"), path);
  if (fclose(f))
    return error_errno(_("writing '%s' failed"), path);

out:
  free(cur.ptr);
  free(result.ptr);
  strbuf_release(&buf);

  return ret;
}

static void update_paths(struct repository *r, struct string_list *update)
{
  struct lock_file index_lock = LOCK_INIT;
  int i;

  repo_hold_locked_index(r, &index_lock, LOCK_DIE_ON_ERROR);

  for (i = 0; i < update->nr; i++) {
    struct string_list_item *item = &update->items[i];
    if (add_file_to_index(r->index, item->string, 0))
      exit(128);
    fprintf_ln(stderr, _("Staged '%s' using previous resolution."),
      item->string);
  }

  if (write_locked_index(r->index, &index_lock,
             COMMIT_LOCK | SKIP_IF_UNCHANGED))
    die(_("unable to write new index file"));
}

static void remove_variant(struct rerere_id *id)
{
  struct strbuf buf = STRBUF_INIT;
  unlink_or_warn(rerere_path(&buf, id, "postimage"));
  unlink_or_warn(rerere_path(&buf, id, "preimage"));
  id->collection->status[id->variant] = 0;
  strbuf_release(&buf);
}

/*
 * The path indicated by rr_item may still have conflict for which we
 * have a recorded resolution, in which case replay it and optionally
 * update it.  Or it may have been resolved by the user and we may
 * only have the preimage for that conflict, in which case the result
 * needs to be recorded as a resolution in a postimage file.
 */
static void do_rerere_one_path(struct index_state *istate,
             struct string_list_item *rr_item,
             struct string_list *update)
{
  const char *path = rr_item->string;
  struct rerere_id *id = rr_item->util;
  struct rerere_dir *rr_dir = id->collection;
  struct strbuf buf = STRBUF_INIT;
  int variant;

  variant = id->variant;

  /* Has the user resolved it already? */
  if (variant >= 0) {
    if (!handle_file(istate, path, NULL, NULL)) {
      copy_file(rerere_path(&buf, id, "postimage"), path, 0666);
      id->collection->status[variant] |= RR_HAS_POSTIMAGE;
      fprintf_ln(stderr, _("Recorded resolution for '%s'."), path);
      free_rerere_id(rr_item);
      rr_item->util = NULL;
      goto out;
    }
    /*
     * There may be other variants that can cleanly
     * replay.  Try them and update the variant number for
     * this one.
     */
  }

  /* Does any existing resolution apply cleanly? */
  for (variant = 0; variant < rr_dir->status_nr; variant++) {
    const int both = RR_HAS_PREIMAGE | RR_HAS_POSTIMAGE;
    struct rerere_id vid = *id;

    if ((rr_dir->status[variant] & both) != both)
      continue;

    vid.variant = variant;
    if (merge(istate, &vid, path))
      continue; /* failed to replay */

    /*
     * If there already is a different variant that applies
     * cleanly, there is no point maintaining our own variant.
     */
    if (0 <= id->variant && id->variant != variant)
      remove_variant(id);

    if (rerere_autoupdate)
      string_list_insert(update, path);
    else
      fprintf_ln(stderr,
           _("Resolved '%s' using previous resolution."),
           path);
    free_rerere_id(rr_item);
    rr_item->util = NULL;
    goto out;
  }

  /* None of the existing one applies; we need a new variant */
  assign_variant(id);

  variant = id->variant;
  handle_file(istate, path, NULL, rerere_path(&buf, id, "preimage"));
  if (id->collection->status[variant] & RR_HAS_POSTIMAGE) {
    const char *path = rerere_path(&buf, id, "postimage");
    if (unlink(path))
      die_errno(_("cannot unlink stray '%s'"), path);
    id->collection->status[variant] &= ~RR_HAS_POSTIMAGE;
  }
  id->collection->status[variant] |= RR_HAS_PREIMAGE;
  fprintf_ln(stderr, _("Recorded preimage for '%s'"), path);

out:
  strbuf_release(&buf);
}

static int do_plain_rerere(struct repository *r,
         struct string_list *rr, int fd)
{
  struct string_list conflict = STRING_LIST_INIT_DUP;
  struct string_list update = STRING_LIST_INIT_DUP;
  struct strbuf buf = STRBUF_INIT;
  int i;

  find_conflict(r, &conflict);

  /*
   * MERGE_RR records paths with conflicts immediately after
   * merge failed.  Some of the conflicted paths might have been
   * hand resolved in the working tree since then, but the
   * initial run would catch all and register their preimages.
   */
  for (i = 0; i < conflict.nr; i++) {
    struct rerere_id *id;
    unsigned char hash[GIT_MAX_RAWSZ];
    const char *path = conflict.items[i].string;
    int ret;

    /*
     * Ask handle_file() to scan and assign a
     * conflict ID.  No need to write anything out
     * yet.
     */
    ret = handle_file(r->index, path, hash, NULL);
    if (ret != 0 && string_list_has_string(rr, path)) {
      remove_variant(string_list_lookup(rr, path)->util);
      string_list_remove(rr, path, 1);
    }
    if (ret < 1)
      continue;

    id = new_rerere_id(hash);
    string_list_insert(rr, path)->util = id;

    /* Ensure that the directory exists. */
    safe_create_dir_in_gitdir(the_repository, rerere_path(&buf, id, NULL));
  }

  for (i = 0; i < rr->nr; i++)
    do_rerere_one_path(r->index, &rr->items[i], &update);

  if (update.nr)
    update_paths(r, &update);

  string_list_clear(&conflict, 0);
  string_list_clear(&update, 0);
  strbuf_release(&buf);
  return write_rr(rr, fd);
}

static void git_rerere_config(void)
{
  repo_config_get_bool(the_repository, "rerere.enabled", &rerere_enabled);
  repo_config_get_bool(the_repository, "rerere.autoupdate", &rerere_autoupdate);
  repo_config(the_repository, git_default_config, NULL);
}

static GIT_PATH_FUNC(git_path_rr_cache, "rr-cache")

static int is_rerere_enabled(void)
{
  int rr_cache_exists;

  if (!rerere_enabled)
    return 0;

  rr_cache_exists = is_directory(git_path_rr_cache());
  if (rerere_enabled < 0)
    return rr_cache_exists;

  if (!rr_cache_exists &&
      safe_create_dir_in_gitdir(the_repository, git_path_rr_cache()))
    die(_("could not create directory '%s'"), git_path_rr_cache());
  return 1;
}

int setup_rerere(struct repository *r, struct string_list *merge_rr, int flags)
{
  int fd;

  git_rerere_config();
  if (!is_rerere_enabled())
    return -1;

  if (flags & (RERERE_AUTOUPDATE|RERERE_NOAUTOUPDATE))
    rerere_autoupdate = !!(flags & RERERE_AUTOUPDATE);
  if (flags & RERERE_READONLY)
    fd = 0;
  else
    fd = hold_lock_file_for_update(&write_lock,
                 git_path_merge_rr(r),
                 LOCK_DIE_ON_ERROR);
  read_rr(r, merge_rr);
  return fd;
}

/*
 * The main entry point that is called internally from codepaths that
 * perform mergy operations, possibly leaving conflicted index entries
 * and working tree files.
 */
int repo_rerere(struct repository *r, int flags)
{
  struct string_list merge_rr = STRING_LIST_INIT_DUP;
  int fd, status;

  fd = setup_rerere(r, &merge_rr, flags);
  if (fd < 0)
    return 0;
  status = do_plain_rerere(r, &merge_rr, fd);
  free_rerere_dirs();
  string_list_clear(&merge_rr, 1);
  return status;
}

/*
 * Subclass of rerere_io that reads from an in-core buffer that is a
 * strbuf
 */
struct rerere_io_mem {
  struct rerere_io io;
  struct strbuf input;
};

/*
 * ... and its getline() method implementation
 */
static int rerere_mem_getline(struct strbuf *sb, struct rerere_io *io_)
{
  struct rerere_io_mem *io = (struct rerere_io_mem *)io_;
  char *ep;
  size_t len;

  strbuf_release(sb);
  if (!io->input.len)
    return -1;
  ep = memchr(io->input.buf, '\n', io->input.len);
  if (!ep)
    ep = io->input.buf + io->input.len;
  else if (*ep == '\n')
    ep++;
  len = ep - io->input.buf;
  strbuf_add(sb, io->input.buf, len);
  strbuf_remove(&io->input, 0, len);
  return 0;
}

static int handle_cache(struct index_state *istate,
      const char *path, unsigned char *hash, const char *output)
{
  mmfile_t mmfile[3] = {{NULL}};
  mmbuffer_t result = {NULL, 0};
  const struct cache_entry *ce;
  int pos, len, i, has_conflicts;
  struct rerere_io_mem io;
  int marker_size = ll_merge_marker_size(istate, path);

  /*
   * Reproduce the conflicted merge in-core
   */
  len = strlen(path);
  pos = index_name_pos(istate, path, len);
  if (0 <= pos)
    return -1;
  pos = -pos - 1;

  while (pos < istate->cache_nr) {
    enum object_type type;
    unsigned long size;

    ce = istate->cache[pos++];
    if (ce_namelen(ce) != len || memcmp(ce->name, path, len))
      break;
    i = ce_stage(ce) - 1;
    if (!mmfile[i].ptr) {
      mmfile[i].ptr = odb_read_object(the_repository->objects,
              &ce->oid, &type, &size);
      if (!mmfile[i].ptr)
        die(_("unable to read %s"),
            oid_to_hex(&ce->oid));
      mmfile[i].size = size;
    }
  }
  for (i = 0; i < 3; i++)
    if (!mmfile[i].ptr && !mmfile[i].size)
      mmfile[i].ptr = xstrdup("");

  /*
   * NEEDSWORK: handle conflicts from merges with
   * merge.renormalize set, too?
   */
  ll_merge(&result, path, &mmfile[0], NULL,
     &mmfile[1], "ours",
     &mmfile[2], "theirs",
     istate, NULL);
  for (i = 0; i < 3; i++)
    free(mmfile[i].ptr);

  memset(&io, 0, sizeof(io));
  io.io.getline = rerere_mem_getline;
  if (output)
    io.io.output = fopen(output, "w");
  else
    io.io.output = NULL;
  strbuf_init(&io.input, 0);
  strbuf_attach(&io.input, result.ptr, result.size, result.size);

  /*
   * Grab the conflict ID and optionally write the original
   * contents with conflict markers out.
   */
  has_conflicts = handle_path(hash, (struct rerere_io *)&io, marker_size);
  strbuf_release(&io.input);
  if (io.io.output)
    fclose(io.io.output);
  return has_conflicts;
}

static int rerere_forget_one_path(struct index_state *istate,
          const char *path,
          struct string_list *rr)
{
  const char *filename;
  struct rerere_id *id;
  unsigned char hash[GIT_MAX_RAWSZ];
  int ret;
  struct strbuf buf = STRBUF_INIT;
  struct string_list_item *item;

  /*
   * Recreate the original conflict from the stages in the
   * index and compute the conflict ID
   */
  ret = handle_cache(istate, path, hash, NULL);
  if (ret < 1)
    return error(_("could not parse conflict hunks in '%s'"), path);

  /* Nuke the recorded resolution for the conflict */
  id = new_rerere_id(hash);

  for (id->variant = 0;
       id->variant < id->collection->status_nr;
       id->variant++) {
    mmfile_t cur = { NULL, 0 };
    mmbuffer_t result = {NULL, 0};
    int cleanly_resolved;

    if (!has_rerere_resolution(id))
      continue;

    handle_cache(istate, path, hash, rerere_path(&buf, id, "thisimage"));
    if (read_mmfile(&cur, rerere_path(&buf, id, "thisimage"))) {
      free(cur.ptr);
      error(_("failed to update conflicted state in '%s'"), path);
      goto fail_exit;
    }
    cleanly_resolved = !try_merge(istate, id, path, &cur, &result);
    free(result.ptr);
    free(cur.ptr);
    if (cleanly_resolved)
      break;
  }

  if (id->collection->status_nr <= id->variant) {
    error(_("no remembered resolution for '%s'"), path);
    goto fail_exit;
  }

  filename = rerere_path(&buf, id, "postimage");
  if (unlink(filename)) {
    if (errno == ENOENT)
      error(_("no remembered resolution for '%s'"), path);
    else
      error_errno(_("cannot unlink '%s'"), filename);
    goto fail_exit;
  }

  /*
   * Update the preimage so that the user can resolve the
   * conflict in the working tree, run us again to record
   * the postimage.
   */
  handle_cache(istate, path, hash, rerere_path(&buf, id, "preimage"));
  fprintf_ln(stderr, _("Updated preimage for '%s'"), path);

  /*
   * And remember that we can record resolution for this
   * conflict when the user is done.
   */
  item = string_list_insert(rr, path);
  free_rerere_id(item);
  item->util = id;
  fprintf(stderr, _("Forgot resolution for '%s'\n"), path);
  strbuf_release(&buf);
  return 0;

fail_exit:
  strbuf_release(&buf);
  free(id);
  return -1;
}

int rerere_forget(struct repository *r, struct pathspec *pathspec)
{
  int i, fd, ret;
  struct string_list conflict = STRING_LIST_INIT_DUP;
  struct string_list merge_rr = STRING_LIST_INIT_DUP;

  if (repo_read_index(r) < 0)
    return error(_("index file corrupt"));

  fd = setup_rerere(r, &merge_rr, RERERE_NOAUTOUPDATE);
  if (fd < 0)
    return 0;

  /*
   * The paths may have been resolved (incorrectly);
   * recover the original conflicted state and then
   * find the conflicted paths.
   */
  unmerge_index(r->index, pathspec, 0);
  find_conflict(r, &conflict);
  for (i = 0; i < conflict.nr; i++) {
    struct string_list_item *it = &conflict.items[i];
    if (!match_pathspec(r->index, pathspec, it->string,
            strlen(it->string), 0, NULL, 0))
      continue;
    rerere_forget_one_path(r->index, it->string, &merge_rr);
  }

  ret = write_rr(&merge_rr, fd);

  string_list_clear(&conflict, 0);
  string_list_clear(&merge_rr, 1);
  return ret;
}

/*
 * Garbage collection support
 */

static timestamp_t rerere_created_at(struct rerere_id *id)
{
  struct strbuf buf = STRBUF_INIT;
  struct stat st;
  timestamp_t ret;

  ret = stat(rerere_path(&buf, id, "preimage"), &st) ? (time_t) 0 : st.st_mtime;

  strbuf_release(&buf);
  return ret;
}

static timestamp_t rerere_last_used_at(struct rerere_id *id)
{
  struct strbuf buf = STRBUF_INIT;
  struct stat st;
  timestamp_t ret;

  ret = stat(rerere_path(&buf, id, "postimage"), &st) ? (time_t) 0 : st.st_mtime;

  strbuf_release(&buf);
  return ret;
}

/*
 * Remove the recorded resolution for a given conflict ID
 */
static void unlink_rr_item(struct rerere_id *id)
{
  struct strbuf buf = STRBUF_INIT;
  unlink_or_warn(rerere_path(&buf, id, "thisimage"));
  remove_variant(id);
  id->collection->status[id->variant] = 0;
  strbuf_release(&buf);
}

static void prune_one(struct rerere_id *id,
          timestamp_t cutoff_resolve, timestamp_t cutoff_noresolve)
{
  timestamp_t then;
  timestamp_t cutoff;

  then = rerere_last_used_at(id);
  if (then)
    cutoff = cutoff_resolve;
  else {
    then = rerere_created_at(id);
    if (!then)
      return;
    cutoff = cutoff_noresolve;
  }
  if (then < cutoff)
    unlink_rr_item(id);
}

/* Does the basename in "path" look plausibly like an rr-cache entry? */
static int is_rr_cache_dirname(const char *path)
{
  struct object_id oid;
  const char *end;
  return !parse_oid_hex(path, &oid, &end) && !*end;
}

void rerere_gc(struct repository *r, struct string_list *rr)
{
  struct string_list to_remove = STRING_LIST_INIT_DUP;
  DIR *dir;
  struct dirent *e;
  int i;
  timestamp_t now = time(NULL);
  timestamp_t cutoff_noresolve = now - 15 * 86400;
  timestamp_t cutoff_resolve = now - 60 * 86400;
  struct strbuf buf = STRBUF_INIT;

  if (setup_rerere(r, rr, 0) < 0)
    return;

  repo_config_get_expiry_in_days(the_repository, "gc.rerereresolved",
               &cutoff_resolve, now);
  repo_config_get_expiry_in_days(the_repository, "gc.rerereunresolved",
               &cutoff_noresolve, now);
  repo_config(the_repository, git_default_config, NULL);
  dir = opendir(repo_git_path_replace(the_repository, &buf, "rr-cache"));
  if (!dir)
    die_errno(_("unable to open rr-cache directory"));
  /* Collect stale conflict IDs ... */
  while ((e = readdir_skip_dot_and_dotdot(dir))) {
    struct rerere_dir *rr_dir;
    struct rerere_id id;
    int now_empty;

    if (!is_rr_cache_dirname(e->d_name))
      continue; /* or should we remove e->d_name? */

    rr_dir = find_rerere_dir(e->d_name);

    now_empty = 1;
    for (id.variant = 0, id.collection = rr_dir;
         id.variant < id.collection->status_nr;
         id.variant++) {
      prune_one(&id, cutoff_resolve, cutoff_noresolve);
      if (id.collection->status[id.variant])
        now_empty = 0;
    }
    if (now_empty)
      string_list_append(&to_remove, e->d_name);
  }
  closedir(dir);

  /* ... and then remove the empty directories */
  for (i = 0; i < to_remove.nr; i++)
    rmdir(repo_git_path_replace(the_repository, &buf,
              "rr-cache/%s", to_remove.items[i].string));

  string_list_clear(&to_remove, 0);
  rollback_lock_file(&write_lock);
  strbuf_release(&buf);
}

/*
 * During a conflict resolution, after "rerere" recorded the
 * preimages, abandon them if the user did not resolve them or
 * record their resolutions.  And drop $GIT_DIR/MERGE_RR.
 *
 * NEEDSWORK: shouldn't we be calling this from "reset --hard"?
 */
void rerere_clear(struct repository *r, struct string_list *merge_rr)
{
  int i;

  if (setup_rerere(r, merge_rr, 0) < 0)
    return;

  for (i = 0; i < merge_rr->nr; i++) {
    struct rerere_id *id = merge_rr->items[i].util;
    struct strbuf buf = STRBUF_INIT;

    if (!has_rerere_resolution(id)) {
      unlink_rr_item(id);
      rmdir(rerere_path(&buf, id, NULL));
    }

    strbuf_release(&buf);
  }
  unlink_or_warn(git_path_merge_rr(r));
  rollback_lock_file(&write_lock);
}

Coverage Report

Created: 2025-12-31 07:01