/src/git/unpack-trees.c

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#define USE_THE_REPOSITORY_VARIABLE

#include "git-compat-util.h"
#include "advice.h"
#include "strvec.h"
#include "repository.h"
#include "parse.h"
#include "dir.h"
#include "environment.h"
#include "gettext.h"
#include "hex.h"
#include "name-hash.h"
#include "tree.h"
#include "tree-walk.h"
#include "cache-tree.h"
#include "unpack-trees.h"
#include "progress.h"
#include "refs.h"
#include "attr.h"
#include "read-cache.h"
#include "split-index.h"
#include "sparse-index.h"
#include "submodule.h"
#include "submodule-config.h"
#include "symlinks.h"
#include "trace2.h"
#include "fsmonitor.h"
#include "object-store-ll.h"
#include "promisor-remote.h"
#include "entry.h"
#include "parallel-checkout.h"
#include "setup.h"

/*
 * Error messages expected by scripts out of plumbing commands such as
 * read-tree.  Non-scripted Porcelain is not required to use these messages
 * and in fact are encouraged to reword them to better suit their particular
 * situation better.  See how "git checkout" and "git merge" replaces
 * them using setup_unpack_trees_porcelain(), for example.
 */
static const char *unpack_plumbing_errors[NB_UNPACK_TREES_WARNING_TYPES] = {
  /* ERROR_WOULD_OVERWRITE */
  "Entry '%s' would be overwritten by merge. Cannot merge.",

  /* ERROR_NOT_UPTODATE_FILE */
  "Entry '%s' not uptodate. Cannot merge.",

  /* ERROR_NOT_UPTODATE_DIR */
  "Updating '%s' would lose untracked files in it",

  /* ERROR_CWD_IN_THE_WAY */
  "Refusing to remove '%s' since it is the current working directory.",

  /* ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN */
  "Untracked working tree file '%s' would be overwritten by merge.",

  /* ERROR_WOULD_LOSE_UNTRACKED_REMOVED */
  "Untracked working tree file '%s' would be removed by merge.",

  /* ERROR_BIND_OVERLAP */
  "Entry '%s' overlaps with '%s'.  Cannot bind.",

  /* ERROR_WOULD_LOSE_SUBMODULE */
  "Submodule '%s' cannot checkout new HEAD.",

  /* NB_UNPACK_TREES_ERROR_TYPES; just a meta value */
  "",

  /* WARNING_SPARSE_NOT_UPTODATE_FILE */
  "Path '%s' not uptodate; will not remove from working tree.",

  /* WARNING_SPARSE_UNMERGED_FILE */
  "Path '%s' unmerged; will not remove from working tree.",

  /* WARNING_SPARSE_ORPHANED_NOT_OVERWRITTEN */
  "Path '%s' already present; will not overwrite with sparse update.",
};

#define ERRORMSG(o,type) \
  ( ((o) && (o)->internal.msgs[(type)]) \
    ? ((o)->internal.msgs[(type)])      \
    : (unpack_plumbing_errors[(type)]) )

static const char *super_prefixed(const char *path, const char *super_prefix)
{
  /*
   * It is necessary and sufficient to have two static buffers
   * here, as the return value of this function is fed to
   * error() using the unpack_*_errors[] templates we see above.
   */
  static struct strbuf buf[2] = {STRBUF_INIT, STRBUF_INIT};
  static int super_prefix_len = -1;
  static unsigned idx = ARRAY_SIZE(buf) - 1;

  if (super_prefix_len < 0) {
    if (!super_prefix) {
      super_prefix_len = 0;
    } else {
      int i;
      for (i = 0; i < ARRAY_SIZE(buf); i++)
        strbuf_addstr(&buf[i], super_prefix);
      super_prefix_len = buf[0].len;
    }
  }

  if (!super_prefix_len)
    return path;

  if (++idx >= ARRAY_SIZE(buf))
    idx = 0;

  strbuf_setlen(&buf[idx], super_prefix_len);
  strbuf_addstr(&buf[idx], path);

  return buf[idx].buf;
}

void setup_unpack_trees_porcelain(struct unpack_trees_options *opts,
          const char *cmd)
{
  int i;
  const char **msgs = opts->internal.msgs;
  const char *msg;

  strvec_init(&opts->internal.msgs_to_free);

  if (!strcmp(cmd, "checkout"))
    msg = advice_enabled(ADVICE_COMMIT_BEFORE_MERGE)
          ? _("Your local changes to the following files would be overwritten by checkout:\n%%s"
        "Please commit your changes or stash them before you switch branches.")
          : _("Your local changes to the following files would be overwritten by checkout:\n%%s");
  else if (!strcmp(cmd, "merge"))
    msg = advice_enabled(ADVICE_COMMIT_BEFORE_MERGE)
          ? _("Your local changes to the following files would be overwritten by merge:\n%%s"
        "Please commit your changes or stash them before you merge.")
          : _("Your local changes to the following files would be overwritten by merge:\n%%s");
  else
    msg = advice_enabled(ADVICE_COMMIT_BEFORE_MERGE)
          ? _("Your local changes to the following files would be overwritten by %s:\n%%s"
        "Please commit your changes or stash them before you %s.")
          : _("Your local changes to the following files would be overwritten by %s:\n%%s");
  msgs[ERROR_WOULD_OVERWRITE] = msgs[ERROR_NOT_UPTODATE_FILE] =
    strvec_pushf(&opts->internal.msgs_to_free, msg, cmd, cmd);

  msgs[ERROR_NOT_UPTODATE_DIR] =
    _("Updating the following directories would lose untracked files in them:\n%s");

  msgs[ERROR_CWD_IN_THE_WAY] =
    _("Refusing to remove the current working directory:\n%s");

  if (!strcmp(cmd, "checkout"))
    msg = advice_enabled(ADVICE_COMMIT_BEFORE_MERGE)
          ? _("The following untracked working tree files would be removed by checkout:\n%%s"
        "Please move or remove them before you switch branches.")
          : _("The following untracked working tree files would be removed by checkout:\n%%s");
  else if (!strcmp(cmd, "merge"))
    msg = advice_enabled(ADVICE_COMMIT_BEFORE_MERGE)
          ? _("The following untracked working tree files would be removed by merge:\n%%s"
        "Please move or remove them before you merge.")
          : _("The following untracked working tree files would be removed by merge:\n%%s");
  else
    msg = advice_enabled(ADVICE_COMMIT_BEFORE_MERGE)
          ? _("The following untracked working tree files would be removed by %s:\n%%s"
        "Please move or remove them before you %s.")
          : _("The following untracked working tree files would be removed by %s:\n%%s");
  msgs[ERROR_WOULD_LOSE_UNTRACKED_REMOVED] =
    strvec_pushf(&opts->internal.msgs_to_free, msg, cmd, cmd);

  if (!strcmp(cmd, "checkout"))
    msg = advice_enabled(ADVICE_COMMIT_BEFORE_MERGE)
          ? _("The following untracked working tree files would be overwritten by checkout:\n%%s"
        "Please move or remove them before you switch branches.")
          : _("The following untracked working tree files would be overwritten by checkout:\n%%s");
  else if (!strcmp(cmd, "merge"))
    msg = advice_enabled(ADVICE_COMMIT_BEFORE_MERGE)
          ? _("The following untracked working tree files would be overwritten by merge:\n%%s"
        "Please move or remove them before you merge.")
          : _("The following untracked working tree files would be overwritten by merge:\n%%s");
  else
    msg = advice_enabled(ADVICE_COMMIT_BEFORE_MERGE)
          ? _("The following untracked working tree files would be overwritten by %s:\n%%s"
        "Please move or remove them before you %s.")
          : _("The following untracked working tree files would be overwritten by %s:\n%%s");
  msgs[ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN] =
    strvec_pushf(&opts->internal.msgs_to_free, msg, cmd, cmd);

  /*
   * Special case: ERROR_BIND_OVERLAP refers to a pair of paths, we
   * cannot easily display it as a list.
   */
  msgs[ERROR_BIND_OVERLAP] = _("Entry '%s' overlaps with '%s'.  Cannot bind.");

  msgs[ERROR_WOULD_LOSE_SUBMODULE] =
    _("Cannot update submodule:\n%s");

  msgs[WARNING_SPARSE_NOT_UPTODATE_FILE] =
    _("The following paths are not up to date and were left despite sparse patterns:\n%s");
  msgs[WARNING_SPARSE_UNMERGED_FILE] =
    _("The following paths are unmerged and were left despite sparse patterns:\n%s");
  msgs[WARNING_SPARSE_ORPHANED_NOT_OVERWRITTEN] =
    _("The following paths were already present and thus not updated despite sparse patterns:\n%s");

  opts->internal.show_all_errors = 1;
  /* rejected paths may not have a static buffer */
  for (i = 0; i < ARRAY_SIZE(opts->internal.unpack_rejects); i++)
    opts->internal.unpack_rejects[i].strdup_strings = 1;
}

void clear_unpack_trees_porcelain(struct unpack_trees_options *opts)
{
  strvec_clear(&opts->internal.msgs_to_free);
  memset(opts->internal.msgs, 0, sizeof(opts->internal.msgs));
  discard_index(&opts->internal.result);
}

static int do_add_entry(struct unpack_trees_options *o, struct cache_entry *ce,
       unsigned int set, unsigned int clear)
{
  clear |= CE_HASHED;

  if (set & CE_REMOVE)
    set |= CE_WT_REMOVE;

  ce->ce_flags = (ce->ce_flags & ~clear) | set;
  return add_index_entry(&o->internal.result, ce,
             ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE);
}

static void add_entry(struct unpack_trees_options *o,
          const struct cache_entry *ce,
          unsigned int set, unsigned int clear)
{
  do_add_entry(o, dup_cache_entry(ce, &o->internal.result), set, clear);
}

/*
 * add error messages on path <path>
 * corresponding to the type <e> with the message <msg>
 * indicating if it should be display in porcelain or not
 */
static int add_rejected_path(struct unpack_trees_options *o,
           enum unpack_trees_error_types e,
           const char *path)
{
  if (o->quiet)
    return -1;

  if (!o->internal.show_all_errors)
    return error(ERRORMSG(o, e), super_prefixed(path,
                  o->super_prefix));

  /*
   * Otherwise, insert in a list for future display by
   * display_(error|warning)_msgs()
   */
  string_list_append(&o->internal.unpack_rejects[e], path);
  return -1;
}

/*
 * display all the error messages stored in a nice way
 */
static void display_error_msgs(struct unpack_trees_options *o)
{
  int e;
  unsigned error_displayed = 0;
  for (e = 0; e < NB_UNPACK_TREES_ERROR_TYPES; e++) {
    struct string_list *rejects = &o->internal.unpack_rejects[e];

    if (rejects->nr > 0) {
      int i;
      struct strbuf path = STRBUF_INIT;

      error_displayed = 1;
      for (i = 0; i < rejects->nr; i++)
        strbuf_addf(&path, "\t%s\n", rejects->items[i].string);
      error(ERRORMSG(o, e), super_prefixed(path.buf,
                   o->super_prefix));
      strbuf_release(&path);
    }
    string_list_clear(rejects, 0);
  }
  if (error_displayed)
    fprintf(stderr, _("Aborting\n"));
}

/*
 * display all the warning messages stored in a nice way
 */
static void display_warning_msgs(struct unpack_trees_options *o)
{
  int e;
  unsigned warning_displayed = 0;
  for (e = NB_UNPACK_TREES_ERROR_TYPES + 1;
       e < NB_UNPACK_TREES_WARNING_TYPES; e++) {
    struct string_list *rejects = &o->internal.unpack_rejects[e];

    if (rejects->nr > 0) {
      int i;
      struct strbuf path = STRBUF_INIT;

      warning_displayed = 1;
      for (i = 0; i < rejects->nr; i++)
        strbuf_addf(&path, "\t%s\n", rejects->items[i].string);
      warning(ERRORMSG(o, e), super_prefixed(path.buf,
                     o->super_prefix));
      strbuf_release(&path);
    }
    string_list_clear(rejects, 0);
  }
  if (warning_displayed)
    fprintf(stderr, _("After fixing the above paths, you may want to run `git sparse-checkout reapply`.\n"));
}
static int check_submodule_move_head(const struct cache_entry *ce,
             const char *old_id,
             const char *new_id,
             struct unpack_trees_options *o)
{
  unsigned flags = SUBMODULE_MOVE_HEAD_DRY_RUN;
  const struct submodule *sub = submodule_from_ce(ce);

  if (!sub)
    return 0;

  if (o->reset)
    flags |= SUBMODULE_MOVE_HEAD_FORCE;

  if (submodule_move_head(ce->name, o->super_prefix, old_id, new_id,
        flags))
    return add_rejected_path(o, ERROR_WOULD_LOSE_SUBMODULE, ce->name);
  return 0;
}

/*
 * Perform the loading of the repository's gitmodules file.  This function is
 * used by 'check_update()' to perform loading of the gitmodules file in two
 * different situations:
 * (1) before removing entries from the working tree if the gitmodules file has
 *     been marked for removal.  This situation is specified by 'state' == NULL.
 * (2) before checking out entries to the working tree if the gitmodules file
 *     has been marked for update.  This situation is specified by 'state' != NULL.
 */
static void load_gitmodules_file(struct index_state *index,
         struct checkout *state)
{
  int pos = index_name_pos(index, GITMODULES_FILE, strlen(GITMODULES_FILE));

  if (pos >= 0) {
    struct cache_entry *ce = index->cache[pos];
    if (!state && ce->ce_flags & CE_WT_REMOVE) {
      repo_read_gitmodules(the_repository, 0);
    } else if (state && (ce->ce_flags & CE_UPDATE)) {
      submodule_free(the_repository);
      checkout_entry(ce, state, NULL, NULL);
      repo_read_gitmodules(the_repository, 0);
    }
  }
}

static struct progress *get_progress(struct unpack_trees_options *o,
             struct index_state *index)
{
  unsigned cnt = 0, total = 0;

  if (!o->update || !o->verbose_update)
    return NULL;

  for (; cnt < index->cache_nr; cnt++) {
    const struct cache_entry *ce = index->cache[cnt];
    if (ce->ce_flags & (CE_UPDATE | CE_WT_REMOVE))
      total++;
  }

  return start_delayed_progress(_("Updating files"), total);
}

static void setup_collided_checkout_detection(struct checkout *state,
                struct index_state *index)
{
  int i;

  state->clone = 1;
  for (i = 0; i < index->cache_nr; i++)
    index->cache[i]->ce_flags &= ~CE_MATCHED;
}

static void report_collided_checkout(struct index_state *index)
{
  struct string_list list = STRING_LIST_INIT_NODUP;
  int i;

  for (i = 0; i < index->cache_nr; i++) {
    struct cache_entry *ce = index->cache[i];

    if (!(ce->ce_flags & CE_MATCHED))
      continue;

    string_list_append(&list, ce->name);
    ce->ce_flags &= ~CE_MATCHED;
  }

  list.cmp = fspathcmp;
  string_list_sort(&list);

  if (list.nr) {
    warning(_("the following paths have collided (e.g. case-sensitive paths\n"
        "on a case-insensitive filesystem) and only one from the same\n"
        "colliding group is in the working tree:\n"));

    for (i = 0; i < list.nr; i++)
      fprintf(stderr, "  '%s'\n", list.items[i].string);
  }

  string_list_clear(&list, 0);
}

static int must_checkout(const struct cache_entry *ce)
{
  return ce->ce_flags & CE_UPDATE;
}

static int check_updates(struct unpack_trees_options *o,
       struct index_state *index)
{
  unsigned cnt = 0;
  int errs = 0;
  struct progress *progress;
  struct checkout state = CHECKOUT_INIT;
  int i, pc_workers, pc_threshold;

  trace_performance_enter();
  state.super_prefix = o->super_prefix;
  state.force = 1;
  state.quiet = 1;
  state.refresh_cache = 1;
  state.istate = index;
  clone_checkout_metadata(&state.meta, &o->meta, NULL);

  if (!o->update || o->dry_run) {
    remove_marked_cache_entries(index, 0);
    trace_performance_leave("check_updates");
    return 0;
  }

  if (o->clone)
    setup_collided_checkout_detection(&state, index);

  progress = get_progress(o, index);

  /* Start with clean cache to avoid using any possibly outdated info. */
  invalidate_lstat_cache();

  git_attr_set_direction(GIT_ATTR_CHECKOUT);

  if (should_update_submodules())
    load_gitmodules_file(index, NULL);

  for (i = 0; i < index->cache_nr; i++) {
    const struct cache_entry *ce = index->cache[i];

    if (ce->ce_flags & CE_WT_REMOVE) {
      display_progress(progress, ++cnt);
      unlink_entry(ce, o->super_prefix);
    }
  }

  remove_marked_cache_entries(index, 0);
  remove_scheduled_dirs();

  if (should_update_submodules())
    load_gitmodules_file(index, &state);

  if (repo_has_promisor_remote(the_repository))
    /*
     * Prefetch the objects that are to be checked out in the loop
     * below.
     */
    prefetch_cache_entries(index, must_checkout);

  get_parallel_checkout_configs(&pc_workers, &pc_threshold);

  enable_delayed_checkout(&state);
  if (pc_workers > 1)
    init_parallel_checkout();
  for (i = 0; i < index->cache_nr; i++) {
    struct cache_entry *ce = index->cache[i];

    if (must_checkout(ce)) {
      size_t last_pc_queue_size = pc_queue_size();

      if (ce->ce_flags & CE_WT_REMOVE)
        BUG("both update and delete flags are set on %s",
            ce->name);
      ce->ce_flags &= ~CE_UPDATE;
      errs |= checkout_entry(ce, &state, NULL, NULL);

      if (last_pc_queue_size == pc_queue_size())
        display_progress(progress, ++cnt);
    }
  }
  if (pc_workers > 1)
    errs |= run_parallel_checkout(&state, pc_workers, pc_threshold,
                progress, &cnt);
  stop_progress(&progress);
  errs |= finish_delayed_checkout(&state, o->verbose_update);
  git_attr_set_direction(GIT_ATTR_CHECKIN);

  if (o->clone)
    report_collided_checkout(index);

  trace_performance_leave("check_updates");
  return errs != 0;
}

static int verify_uptodate_sparse(const struct cache_entry *ce,
          struct unpack_trees_options *o);
static int verify_absent_sparse(const struct cache_entry *ce,
        enum unpack_trees_error_types,
        struct unpack_trees_options *o);

static int apply_sparse_checkout(struct index_state *istate,
         struct cache_entry *ce,
         struct unpack_trees_options *o)
{
  int was_skip_worktree = ce_skip_worktree(ce);

  if (ce->ce_flags & CE_NEW_SKIP_WORKTREE)
    ce->ce_flags |= CE_SKIP_WORKTREE;
  else
    ce->ce_flags &= ~CE_SKIP_WORKTREE;
  if (was_skip_worktree != ce_skip_worktree(ce)) {
    ce->ce_flags |= CE_UPDATE_IN_BASE;
    mark_fsmonitor_invalid(istate, ce);
    istate->cache_changed |= CE_ENTRY_CHANGED;
  }

  /*
   * if (!was_skip_worktree && !ce_skip_worktree()) {
   *  This is perfectly normal. Move on;
   * }
   */

  /*
   * Merge strategies may set CE_UPDATE|CE_REMOVE outside checkout
   * area as a result of ce_skip_worktree() shortcuts in
   * verify_absent() and verify_uptodate().
   * Make sure they don't modify worktree if they are already
   * outside checkout area
   */
  if (was_skip_worktree && ce_skip_worktree(ce)) {
    ce->ce_flags &= ~CE_UPDATE;

    /*
     * By default, when CE_REMOVE is on, CE_WT_REMOVE is also
     * on to get that file removed from both index and worktree.
     * If that file is already outside worktree area, don't
     * bother remove it.
     */
    if (ce->ce_flags & CE_REMOVE)
      ce->ce_flags &= ~CE_WT_REMOVE;
  }

  if (!was_skip_worktree && ce_skip_worktree(ce)) {
    /*
     * If CE_UPDATE is set, verify_uptodate() must be called already
     * also stat info may have lost after merged_entry() so calling
     * verify_uptodate() again may fail
     */
    if (!(ce->ce_flags & CE_UPDATE) &&
        verify_uptodate_sparse(ce, o)) {
      ce->ce_flags &= ~CE_SKIP_WORKTREE;
      return -1;
    }
    ce->ce_flags |= CE_WT_REMOVE;
    ce->ce_flags &= ~CE_UPDATE;
  }
  if (was_skip_worktree && !ce_skip_worktree(ce)) {
    if (verify_absent_sparse(ce, WARNING_SPARSE_ORPHANED_NOT_OVERWRITTEN, o))
      return -1;
    ce->ce_flags |= CE_UPDATE;
  }
  return 0;
}

static int warn_conflicted_path(struct index_state *istate,
        int i,
        struct unpack_trees_options *o)
{
  char *conflicting_path = istate->cache[i]->name;
  int count = 0;

  add_rejected_path(o, WARNING_SPARSE_UNMERGED_FILE, conflicting_path);

  /* Find out how many higher stage entries are at same path */
  while ((++count) + i < istate->cache_nr &&
         !strcmp(conflicting_path, istate->cache[count + i]->name))
    ; /* do nothing */

  return count;
}

static inline int call_unpack_fn(const struct cache_entry * const *src,
         struct unpack_trees_options *o)
{
  int ret = o->fn(src, o);
  if (ret > 0)
    ret = 0;
  return ret;
}

static void mark_ce_used(struct cache_entry *ce, struct unpack_trees_options *o)
{
  ce->ce_flags |= CE_UNPACKED;

  if (o->internal.cache_bottom < o->src_index->cache_nr &&
      o->src_index->cache[o->internal.cache_bottom] == ce) {
    int bottom = o->internal.cache_bottom;

    while (bottom < o->src_index->cache_nr &&
           o->src_index->cache[bottom]->ce_flags & CE_UNPACKED)
      bottom++;
    o->internal.cache_bottom = bottom;
  }
}

static void mark_all_ce_unused(struct index_state *index)
{
  int i;
  for (i = 0; i < index->cache_nr; i++)
    index->cache[i]->ce_flags &= ~(CE_UNPACKED | CE_ADDED | CE_NEW_SKIP_WORKTREE);
}

static int locate_in_src_index(const struct cache_entry *ce,
             struct unpack_trees_options *o)
{
  struct index_state *index = o->src_index;
  int len = ce_namelen(ce);
  int pos = index_name_pos(index, ce->name, len);
  if (pos < 0)
    pos = -1 - pos;
  return pos;
}

/*
 * We call unpack_index_entry() with an unmerged cache entry
 * only in diff-index, and it wants a single callback.  Skip
 * the other unmerged entry with the same name.
 */
static void mark_ce_used_same_name(struct cache_entry *ce,
           struct unpack_trees_options *o)
{
  struct index_state *index = o->src_index;
  int len = ce_namelen(ce);
  int pos;

  for (pos = locate_in_src_index(ce, o); pos < index->cache_nr; pos++) {
    struct cache_entry *next = index->cache[pos];
    if (len != ce_namelen(next) ||
        memcmp(ce->name, next->name, len))
      break;
    mark_ce_used(next, o);
  }
}

static struct cache_entry *next_cache_entry(struct unpack_trees_options *o)
{
  const struct index_state *index = o->src_index;
  int pos = o->internal.cache_bottom;

  while (pos < index->cache_nr) {
    struct cache_entry *ce = index->cache[pos];
    if (!(ce->ce_flags & CE_UNPACKED))
      return ce;
    pos++;
  }
  return NULL;
}

static void add_same_unmerged(const struct cache_entry *ce,
            struct unpack_trees_options *o)
{
  struct index_state *index = o->src_index;
  int len = ce_namelen(ce);
  int pos = index_name_pos(index, ce->name, len);

  if (0 <= pos)
    die("programming error in a caller of mark_ce_used_same_name");
  for (pos = -pos - 1; pos < index->cache_nr; pos++) {
    struct cache_entry *next = index->cache[pos];
    if (len != ce_namelen(next) ||
        memcmp(ce->name, next->name, len))
      break;
    add_entry(o, next, 0, 0);
    mark_ce_used(next, o);
  }
}

static int unpack_index_entry(struct cache_entry *ce,
            struct unpack_trees_options *o)
{
  const struct cache_entry *src[MAX_UNPACK_TREES + 1] = { NULL, };
  int ret;

  src[0] = ce;

  mark_ce_used(ce, o);
  if (ce_stage(ce)) {
    if (o->skip_unmerged) {
      add_entry(o, ce, 0, 0);
      return 0;
    }
  }
  ret = call_unpack_fn(src, o);
  if (ce_stage(ce))
    mark_ce_used_same_name(ce, o);
  return ret;
}

static int find_cache_pos(struct traverse_info *, const char *p, size_t len);

static void restore_cache_bottom(struct traverse_info *info, int bottom)
{
  struct unpack_trees_options *o = info->data;

  if (o->diff_index_cached)
    return;
  o->internal.cache_bottom = bottom;
}

static int switch_cache_bottom(struct traverse_info *info)
{
  struct unpack_trees_options *o = info->data;
  int ret, pos;

  if (o->diff_index_cached)
    return 0;
  ret = o->internal.cache_bottom;
  pos = find_cache_pos(info->prev, info->name, info->namelen);

  if (pos < -1)
    o->internal.cache_bottom = -2 - pos;
  else if (pos < 0)
    o->internal.cache_bottom = o->src_index->cache_nr;
  return ret;
}

static inline int are_same_oid(struct name_entry *name_j, struct name_entry *name_k)
{
  return !is_null_oid(&name_j->oid) && !is_null_oid(&name_k->oid) && oideq(&name_j->oid, &name_k->oid);
}

static int all_trees_same_as_cache_tree(int n, unsigned long dirmask,
          struct name_entry *names,
          struct traverse_info *info)
{
  struct unpack_trees_options *o = info->data;
  int i;

  if (!o->merge || dirmask != ((1 << n) - 1))
    return 0;

  for (i = 1; i < n; i++)
    if (!are_same_oid(names, names + i))
      return 0;

  return cache_tree_matches_traversal(o->src_index->cache_tree, names, info);
}

static int index_pos_by_traverse_info(struct name_entry *names,
              struct traverse_info *info)
{
  struct unpack_trees_options *o = info->data;
  struct strbuf name = STRBUF_INIT;
  int pos;

  strbuf_make_traverse_path(&name, info, names->path, names->pathlen);
  strbuf_addch(&name, '/');
  pos = index_name_pos(o->src_index, name.buf, name.len);
  if (pos >= 0) {
    if (!o->src_index->sparse_index ||
        !(o->src_index->cache[pos]->ce_flags & CE_SKIP_WORKTREE))
      BUG("This is a directory and should not exist in index");
  } else {
    pos = -pos - 1;
  }
  if (pos >= o->src_index->cache_nr ||
      !starts_with(o->src_index->cache[pos]->name, name.buf) ||
      (pos > 0 && starts_with(o->src_index->cache[pos-1]->name, name.buf)))
    BUG("pos %d doesn't point to the first entry of %s in index",
        pos, name.buf);
  strbuf_release(&name);
  return pos;
}

/*
 * Fast path if we detect that all trees are the same as cache-tree at this
 * path. We'll walk these trees in an iterative loop using cache-tree/index
 * instead of ODB since we already know what these trees contain.
 */
static int traverse_by_cache_tree(int pos, int nr_entries, int nr_names,
          struct traverse_info *info)
{
  struct cache_entry *src[MAX_UNPACK_TREES + 1] = { NULL, };
  struct unpack_trees_options *o = info->data;
  struct cache_entry *tree_ce = NULL;
  int ce_len = 0;
  int i, d;

  if (!o->merge)
    BUG("We need cache-tree to do this optimization");

  /*
   * Do what unpack_callback() and unpack_single_entry() normally
   * do. But we walk all paths in an iterative loop instead.
   *
   * D/F conflicts and higher stage entries are not a concern
   * because cache-tree would be invalidated and we would never
   * get here in the first place.
   */
  for (i = 0; i < nr_entries; i++) {
    int new_ce_len, len, rc;

    src[0] = o->src_index->cache[pos + i];

    len = ce_namelen(src[0]);
    new_ce_len = cache_entry_size(len);

    if (new_ce_len > ce_len) {
      new_ce_len <<= 1;
      tree_ce = xrealloc(tree_ce, new_ce_len);
      memset(tree_ce, 0, new_ce_len);
      ce_len = new_ce_len;

      tree_ce->ce_flags = create_ce_flags(0);

      for (d = 1; d <= nr_names; d++)
        src[d] = tree_ce;
    }

    tree_ce->ce_mode = src[0]->ce_mode;
    tree_ce->ce_namelen = len;
    oidcpy(&tree_ce->oid, &src[0]->oid);
    memcpy(tree_ce->name, src[0]->name, len + 1);

    rc = call_unpack_fn((const struct cache_entry * const *)src, o);
    if (rc < 0) {
      free(tree_ce);
      return rc;
    }

    mark_ce_used(src[0], o);
  }
  free(tree_ce);
  if (o->internal.debug_unpack)
    printf("Unpacked %d entries from %s to %s using cache-tree\n",
           nr_entries,
           o->src_index->cache[pos]->name,
           o->src_index->cache[pos + nr_entries - 1]->name);
  return 0;
}

static int traverse_trees_recursive(int n, unsigned long dirmask,
            unsigned long df_conflicts,
            struct name_entry *names,
            struct traverse_info *info)
{
  struct unpack_trees_options *o = info->data;
  int i, ret, bottom;
  int nr_buf = 0;
  struct tree_desc *t;
  void **buf;
  struct traverse_info newinfo;
  struct name_entry *p;
  int nr_entries;

  nr_entries = all_trees_same_as_cache_tree(n, dirmask, names, info);
  if (nr_entries > 0) {
    int pos = index_pos_by_traverse_info(names, info);

    if (!o->merge || df_conflicts)
      BUG("Wrong condition to get here buddy");

    /*
     * All entries up to 'pos' must have been processed
     * (i.e. marked CE_UNPACKED) at this point. But to be safe,
     * save and restore cache_bottom anyway to not miss
     * unprocessed entries before 'pos'.
     */
    bottom = o->internal.cache_bottom;
    ret = traverse_by_cache_tree(pos, nr_entries, n, info);
    o->internal.cache_bottom = bottom;
    return ret;
  }

  p = names;
  while (!p->mode)
    p++;

  newinfo = *info;
  newinfo.prev = info;
  newinfo.pathspec = info->pathspec;
  newinfo.name = p->path;
  newinfo.namelen = p->pathlen;
  newinfo.mode = p->mode;
  newinfo.pathlen = st_add3(newinfo.pathlen, tree_entry_len(p), 1);
  newinfo.df_conflicts |= df_conflicts;

  ALLOC_ARRAY(t, n);
  ALLOC_ARRAY(buf, n);

  /*
   * Fetch the tree from the ODB for each peer directory in the
   * n commits.
   *
   * For 2- and 3-way traversals, we try to avoid hitting the
   * ODB twice for the same OID.  This should yield a nice speed
   * up in checkouts and merges when the commits are similar.
   *
   * We don't bother doing the full O(n^2) search for larger n,
   * because wider traversals don't happen that often and we
   * avoid the search setup.
   *
   * When 2 peer OIDs are the same, we just copy the tree
   * descriptor data.  This implicitly borrows the buffer
   * data from the earlier cell.
   */
  for (i = 0; i < n; i++, dirmask >>= 1) {
    if (i > 0 && are_same_oid(&names[i], &names[i - 1]))
      t[i] = t[i - 1];
    else if (i > 1 && are_same_oid(&names[i], &names[i - 2]))
      t[i] = t[i - 2];
    else {
      const struct object_id *oid = NULL;
      if (dirmask & 1)
        oid = &names[i].oid;
      buf[nr_buf++] = fill_tree_descriptor(the_repository, t + i, oid);
    }
  }

  bottom = switch_cache_bottom(&newinfo);
  ret = traverse_trees(o->src_index, n, t, &newinfo);
  restore_cache_bottom(&newinfo, bottom);

  for (i = 0; i < nr_buf; i++)
    free(buf[i]);
  free(buf);
  free(t);

  return ret;
}

/*
 * Compare the traverse-path to the cache entry without actually
 * having to generate the textual representation of the traverse
 * path.
 *
 * NOTE! This *only* compares up to the size of the traverse path
 * itself - the caller needs to do the final check for the cache
 * entry having more data at the end!
 */
static int do_compare_entry_piecewise(const struct cache_entry *ce,
              const struct traverse_info *info,
              const char *name, size_t namelen,
              unsigned mode)
{
  int pathlen, ce_len;
  const char *ce_name;

  if (info->prev) {
    int cmp = do_compare_entry_piecewise(ce, info->prev,
                 info->name, info->namelen,
                 info->mode);
    if (cmp)
      return cmp;
  }
  pathlen = info->pathlen;
  ce_len = ce_namelen(ce);

  /* If ce_len < pathlen then we must have previously hit "name == directory" entry */
  if (ce_len < pathlen)
    return -1;

  ce_len -= pathlen;
  ce_name = ce->name + pathlen;

  return df_name_compare(ce_name, ce_len, S_IFREG, name, namelen, mode);
}

static int do_compare_entry(const struct cache_entry *ce,
          const struct traverse_info *info,
          const char *name, size_t namelen,
          unsigned mode)
{
  int pathlen, ce_len;
  const char *ce_name;
  int cmp;
  unsigned ce_mode;

  /*
   * If we have not precomputed the traverse path, it is quicker
   * to avoid doing so.  But if we have precomputed it,
   * it is quicker to use the precomputed version.
   */
  if (!info->traverse_path)
    return do_compare_entry_piecewise(ce, info, name, namelen, mode);

  cmp = strncmp(ce->name, info->traverse_path, info->pathlen);
  if (cmp)
    return cmp;

  pathlen = info->pathlen;
  ce_len = ce_namelen(ce);

  if (ce_len < pathlen)
    return -1;

  ce_len -= pathlen;
  ce_name = ce->name + pathlen;

  ce_mode = S_ISSPARSEDIR(ce->ce_mode) ? S_IFDIR : S_IFREG;
  return df_name_compare(ce_name, ce_len, ce_mode, name, namelen, mode);
}

static int compare_entry(const struct cache_entry *ce, const struct traverse_info *info, const struct name_entry *n)
{
  int cmp = do_compare_entry(ce, info, n->path, n->pathlen, n->mode);
  if (cmp)
    return cmp;

  /*
   * At this point, we know that we have a prefix match. If ce
   * is a sparse directory, then allow an exact match. This only
   * works when the input name is a directory, since ce->name
   * ends in a directory separator.
   */
  if (S_ISSPARSEDIR(ce->ce_mode) &&
      ce->ce_namelen == traverse_path_len(info, tree_entry_len(n)) + 1)
    return 0;

  /*
   * Even if the beginning compared identically, the ce should
   * compare as bigger than a directory leading up to it!
   */
  return ce_namelen(ce) > traverse_path_len(info, tree_entry_len(n));
}

static int ce_in_traverse_path(const struct cache_entry *ce,
             const struct traverse_info *info)
{
  if (!info->prev)
    return 1;
  if (do_compare_entry(ce, info->prev,
           info->name, info->namelen, info->mode))
    return 0;
  /*
   * If ce (blob) is the same name as the path (which is a tree
   * we will be descending into), it won't be inside it.
   */
  return (info->pathlen < ce_namelen(ce));
}

static struct cache_entry *create_ce_entry(const struct traverse_info *info,
  const struct name_entry *n,
  int stage,
  struct index_state *istate,
  int is_transient,
  int is_sparse_directory)
{
  size_t len = traverse_path_len(info, tree_entry_len(n));
  size_t alloc_len = is_sparse_directory ? len + 1 : len;
  struct cache_entry *ce =
    is_transient ?
    make_empty_transient_cache_entry(alloc_len, NULL) :
    make_empty_cache_entry(istate, alloc_len);

  ce->ce_mode = create_ce_mode(n->mode);
  ce->ce_flags = create_ce_flags(stage);
  ce->ce_namelen = len;
  oidcpy(&ce->oid, &n->oid);
  /* len+1 because the cache_entry allocates space for NUL */
  make_traverse_path(ce->name, len + 1, info, n->path, n->pathlen);

  if (is_sparse_directory) {
    ce->name[len] = '/';
    ce->name[len + 1] = '\0';
    ce->ce_namelen++;
    ce->ce_flags |= CE_SKIP_WORKTREE;
  }

  return ce;
}

/*
 * Determine whether the path specified by 'p' should be unpacked as a new
 * sparse directory in a sparse index. A new sparse directory 'A/':
 * - must be outside the sparse cone.
 * - must not already be in the index (i.e., no index entry with name 'A/'
 *   exists).
 * - must not have any child entries in the index (i.e., no index entry
 *   'A/<something>' exists).
 * If 'p' meets the above requirements, return 1; otherwise, return 0.
 */
static int entry_is_new_sparse_dir(const struct traverse_info *info,
           const struct name_entry *p)
{
  int res, pos;
  struct strbuf dirpath = STRBUF_INIT;
  struct unpack_trees_options *o = info->data;

  if (!S_ISDIR(p->mode))
    return 0;

  /*
   * If the path is inside the sparse cone, it can't be a sparse directory.
   */
  strbuf_add(&dirpath, info->traverse_path, info->pathlen);
  strbuf_add(&dirpath, p->path, p->pathlen);
  strbuf_addch(&dirpath, '/');
  if (path_in_cone_mode_sparse_checkout(dirpath.buf, o->src_index)) {
    res = 0;
    goto cleanup;
  }

  pos = index_name_pos_sparse(o->src_index, dirpath.buf, dirpath.len);
  if (pos >= 0) {
    /* Path is already in the index, not a new sparse dir */
    res = 0;
    goto cleanup;
  }

  /* Where would this sparse dir be inserted into the index? */
  pos = -pos - 1;
  if (pos >= o->src_index->cache_nr) {
    /*
     * Sparse dir would be inserted at the end of the index, so we
     * know it has no child entries.
     */
    res = 1;
    goto cleanup;
  }

  /*
   * If the dir has child entries in the index, the first would be at the
   * position the sparse directory would be inserted. If the entry at this
   * position is inside the dir, not a new sparse dir.
   */
  res = strncmp(o->src_index->cache[pos]->name, dirpath.buf, dirpath.len);

cleanup:
  strbuf_release(&dirpath);
  return res;
}

/*
 * Note that traverse_by_cache_tree() duplicates some logic in this function
 * without actually calling it. If you change the logic here you may need to
 * check and change there as well.
 */
static int unpack_single_entry(int n, unsigned long mask,
             unsigned long dirmask,
             struct cache_entry **src,
             const struct name_entry *names,
             const struct traverse_info *info,
             int *is_new_sparse_dir)
{
  int i;
  struct unpack_trees_options *o = info->data;
  unsigned long conflicts = info->df_conflicts | dirmask;
  const struct name_entry *p = names;

  *is_new_sparse_dir = 0;
  if (mask == dirmask && !src[0]) {
    /*
     * If we're not in a sparse index, we can't unpack a directory
     * without recursing into it, so we return.
     */
    if (!o->src_index->sparse_index)
      return 0;

    /* Find first entry with a real name (we could use "mask" too) */
    while (!p->mode)
      p++;

    /*
     * If the directory is completely missing from the index but
     * would otherwise be a sparse directory, we should unpack it.
     * If not, we'll return and continue recursively traversing the
     * tree.
     */
    *is_new_sparse_dir = entry_is_new_sparse_dir(info, p);
    if (!*is_new_sparse_dir)
      return 0;
  }

  /*
   * When we are unpacking a sparse directory, then this isn't necessarily
   * a directory-file conflict.
   */
  if (mask == dirmask &&
      (*is_new_sparse_dir || (src[0] && S_ISSPARSEDIR(src[0]->ce_mode))))
    conflicts = 0;

  /*
   * Ok, we've filled in up to any potential index entry in src[0],
   * now do the rest.
   */
  for (i = 0; i < n; i++) {
    int stage;
    unsigned int bit = 1ul << i;
    if (conflicts & bit) {
      src[i + o->merge] = o->df_conflict_entry;
      continue;
    }
    if (!(mask & bit))
      continue;
    if (!o->merge)
      stage = 0;
    else if (i + 1 < o->head_idx)
      stage = 1;
    else if (i + 1 > o->head_idx)
      stage = 3;
    else
      stage = 2;

    /*
     * If the merge bit is set, then the cache entries are
     * discarded in the following block.  In this case,
     * construct "transient" cache_entries, as they are
     * not stored in the index.  otherwise construct the
     * cache entry from the index aware logic.
     */
    src[i + o->merge] = create_ce_entry(info, names + i, stage,
                &o->internal.result,
                o->merge, bit & dirmask);
  }

  if (o->merge) {
    int rc = call_unpack_fn((const struct cache_entry * const *)src,
          o);
    for (i = 0; i < n; i++) {
      struct cache_entry *ce = src[i + o->merge];
      if (ce != o->df_conflict_entry)
        discard_cache_entry(ce);
    }
    return rc;
  }

  for (i = 0; i < n; i++)
    if (src[i] && src[i] != o->df_conflict_entry)
      if (do_add_entry(o, src[i], 0, 0))
        return -1;

  return 0;
}

static int unpack_failed(struct unpack_trees_options *o, const char *message)
{
  discard_index(&o->internal.result);
  if (!o->quiet && !o->exiting_early) {
    if (message)
      return error("%s", message);
    return -1;
  }
  return -1;
}

/*
 * The tree traversal is looking at name p.  If we have a matching entry,
 * return it.  If name p is a directory in the index, do not return
 * anything, as we will want to match it when the traversal descends into
 * the directory.
 */
static int find_cache_pos(struct traverse_info *info,
        const char *p, size_t p_len)
{
  int pos;
  struct unpack_trees_options *o = info->data;
  struct index_state *index = o->src_index;
  int pfxlen = info->pathlen;

  for (pos = o->internal.cache_bottom; pos < index->cache_nr; pos++) {
    const struct cache_entry *ce = index->cache[pos];
    const char *ce_name, *ce_slash;
    int cmp, ce_len;

    if (ce->ce_flags & CE_UNPACKED) {
      /*
       * cache_bottom entry is already unpacked, so
       * we can never match it; don't check it
       * again.
       */
      if (pos == o->internal.cache_bottom)
        ++o->internal.cache_bottom;
      continue;
    }
    if (!ce_in_traverse_path(ce, info)) {
      /*
       * Check if we can skip future cache checks
       * (because we're already past all possible
       * entries in the traverse path).
       */
      if (info->traverse_path) {
        if (strncmp(ce->name, info->traverse_path,
              info->pathlen) > 0)
          break;
      }
      continue;
    }
    ce_name = ce->name + pfxlen;
    ce_slash = strchr(ce_name, '/');
    if (ce_slash)
      ce_len = ce_slash - ce_name;
    else
      ce_len = ce_namelen(ce) - pfxlen;
    cmp = name_compare(p, p_len, ce_name, ce_len);
    /*
     * Exact match; if we have a directory we need to
     * delay returning it.
     */
    if (!cmp)
      return ce_slash ? -2 - pos : pos;
    if (0 < cmp)
      continue; /* keep looking */
    /*
     * ce_name sorts after p->path; could it be that we
     * have files under p->path directory in the index?
     * E.g.  ce_name == "t-i", and p->path == "t"; we may
     * have "t/a" in the index.
     */
    if (p_len < ce_len && !memcmp(ce_name, p, p_len) &&
        ce_name[p_len] < '/')
      continue; /* keep looking */
    break;
  }
  return -1;
}

/*
 * Given a sparse directory entry 'ce', compare ce->name to
 * info->traverse_path + p->path + '/' if info->traverse_path
 * is non-empty.
 *
 * Compare ce->name to p->path + '/' otherwise. Note that
 * ce->name must end in a trailing '/' because it is a sparse
 * directory entry.
 */
static int sparse_dir_matches_path(const struct cache_entry *ce,
           struct traverse_info *info,
           const struct name_entry *p)
{
  assert(S_ISSPARSEDIR(ce->ce_mode));
  assert(ce->name[ce->ce_namelen - 1] == '/');

  if (info->pathlen)
    return ce->ce_namelen == info->pathlen + p->pathlen + 1 &&
           ce->name[info->pathlen - 1] == '/' &&
           !strncmp(ce->name, info->traverse_path, info->pathlen) &&
           !strncmp(ce->name + info->pathlen, p->path, p->pathlen);
  return ce->ce_namelen == p->pathlen + 1 &&
         !strncmp(ce->name, p->path, p->pathlen);
}

static struct cache_entry *find_cache_entry(struct traverse_info *info,
              const struct name_entry *p)
{
  const char *path;
  int pos = find_cache_pos(info, p->path, p->pathlen);
  struct unpack_trees_options *o = info->data;

  if (0 <= pos)
    return o->src_index->cache[pos];

  /*
   * Check for a sparse-directory entry named "path/".
   * Due to the input p->path not having a trailing
   * slash, the negative 'pos' value overshoots the
   * expected position, hence "-2" instead of "-1".
   */
  pos = -pos - 2;

  if (pos < 0 || pos >= o->src_index->cache_nr)
    return NULL;

  /*
   * Due to lexicographic sorting and sparse directory
   * entries ending with a trailing slash, our path as a
   * sparse directory (e.g "subdir/") and our path as a
   * file (e.g. "subdir") might be separated by other
   * paths (e.g. "subdir-").
   */
  while (pos >= 0) {
    struct cache_entry *ce = o->src_index->cache[pos];

    if (!skip_prefix(ce->name, info->traverse_path, &path) ||
        strncmp(path, p->path, p->pathlen) ||
        path[p->pathlen] != '/')
      return NULL;

    if (S_ISSPARSEDIR(ce->ce_mode) &&
        sparse_dir_matches_path(ce, info, p))
      return ce;

    pos--;
  }

  return NULL;
}

static void debug_path(struct traverse_info *info)
{
  if (info->prev) {
    debug_path(info->prev);
    if (*info->prev->name)
      putchar('/');
  }
  printf("%s", info->name);
}

static void debug_name_entry(int i, struct name_entry *n)
{
  printf("ent#%d %06o %s\n", i,
         n->path ? n->mode : 0,
         n->path ? n->path : "(missing)");
}

static void debug_unpack_callback(int n,
          unsigned long mask,
          unsigned long dirmask,
          struct name_entry *names,
          struct traverse_info *info)
{
  int i;
  printf("* unpack mask %lu, dirmask %lu, cnt %d ",
         mask, dirmask, n);
  debug_path(info);
  putchar('\n');
  for (i = 0; i < n; i++)
    debug_name_entry(i, names + i);
}

/*
 * Returns true if and only if the given cache_entry is a
 * sparse-directory entry that matches the given name_entry
 * from the tree walk at the given traverse_info.
 */
static int is_sparse_directory_entry(struct cache_entry *ce,
             const struct name_entry *name,
             struct traverse_info *info)
{
  if (!ce || !name || !S_ISSPARSEDIR(ce->ce_mode))
    return 0;

  return sparse_dir_matches_path(ce, info, name);
}

static int unpack_sparse_callback(int n, unsigned long mask, unsigned long dirmask, struct name_entry *names, struct traverse_info *info)
{
  struct cache_entry *src[MAX_UNPACK_TREES + 1] = { NULL, };
  struct unpack_trees_options *o = info->data;
  int ret, is_new_sparse_dir;

  assert(o->merge);

  /*
   * Unlike in 'unpack_callback', where src[0] is derived from the index when
   * merging, src[0] is a transient cache entry derived from the first tree
   * provided. Create the temporary entry as if it came from a non-sparse index.
   */
  if (!is_null_oid(&names[0].oid)) {
    src[0] = create_ce_entry(info, &names[0], 0,
          &o->internal.result, 1,
          dirmask & (1ul << 0));
    src[0]->ce_flags |= (CE_SKIP_WORKTREE | CE_NEW_SKIP_WORKTREE);
  }

  /*
   * 'unpack_single_entry' assumes that src[0] is derived directly from
   * the index, rather than from an entry in 'names'. This is *not* true when
   * merging a sparse directory, in which case names[0] is the "index" source
   * entry. To match the expectations of 'unpack_single_entry', shift past the
   * "index" tree (i.e., names[0]) and adjust 'names', 'n', 'mask', and
   * 'dirmask' accordingly.
   */
  ret = unpack_single_entry(n - 1, mask >> 1, dirmask >> 1, src, names + 1, info, &is_new_sparse_dir);

  if (src[0])
    discard_cache_entry(src[0]);

  return ret >= 0 ? mask : -1;
}

/*
 * Note that traverse_by_cache_tree() duplicates some logic in this function
 * without actually calling it. If you change the logic here you may need to
 * check and change there as well.
 */
static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, struct name_entry *names, struct traverse_info *info)
{
  struct cache_entry *src[MAX_UNPACK_TREES + 1] = { NULL, };
  struct unpack_trees_options *o = info->data;
  const struct name_entry *p = names;
  int is_new_sparse_dir;

  /* Find first entry with a real name (we could use "mask" too) */
  while (!p->mode)
    p++;

  if (o->internal.debug_unpack)
    debug_unpack_callback(n, mask, dirmask, names, info);

  /* Are we supposed to look at the index too? */
  if (o->merge) {
    while (1) {
      int cmp;
      struct cache_entry *ce;

      if (o->diff_index_cached)
        ce = next_cache_entry(o);
      else
        ce = find_cache_entry(info, p);

      if (!ce)
        break;
      cmp = compare_entry(ce, info, p);
      if (cmp < 0) {
        if (unpack_index_entry(ce, o) < 0)
          return unpack_failed(o, NULL);
        continue;
      }
      if (!cmp) {
        if (ce_stage(ce)) {
          /*
           * If we skip unmerged index
           * entries, we'll skip this
           * entry *and* the tree
           * entries associated with it!
           */
          if (o->skip_unmerged) {
            add_same_unmerged(ce, o);
            return mask;
          }
        }
        src[0] = ce;
      }
      break;
    }
  }

  if (unpack_single_entry(n, mask, dirmask, src, names, info, &is_new_sparse_dir))
    return -1;

  if (o->merge && src[0]) {
    if (ce_stage(src[0]))
      mark_ce_used_same_name(src[0], o);
    else
      mark_ce_used(src[0], o);
  }

  /* Now handle any directories.. */
  if (dirmask) {
    /* special case: "diff-index --cached" looking at a tree */
    if (o->diff_index_cached &&
        n == 1 && dirmask == 1 && S_ISDIR(names->mode)) {
      int matches;
      matches = cache_tree_matches_traversal(o->src_index->cache_tree,
                     names, info);
      /*
       * Everything under the name matches; skip the
       * entire hierarchy.  diff_index_cached codepath
       * special cases D/F conflicts in such a way that
       * it does not do any look-ahead, so this is safe.
       */
      if (matches) {
        /*
         * Only increment the cache_bottom if the
         * directory isn't a sparse directory index
         * entry (if it is, it was already incremented)
         * in 'mark_ce_used()'
         */
        if (!src[0] || !S_ISSPARSEDIR(src[0]->ce_mode))
          o->internal.cache_bottom += matches;
        return mask;
      }
    }

    if (!is_sparse_directory_entry(src[0], p, info) &&
        !is_new_sparse_dir &&
        traverse_trees_recursive(n, dirmask, mask & ~dirmask,
                names, info) < 0) {
      return -1;
    }

    return mask;
  }

  return mask;
}

static int clear_ce_flags_1(struct index_state *istate,
          struct cache_entry **cache, int nr,
          struct strbuf *prefix,
          int select_mask, int clear_mask,
          struct pattern_list *pl,
          enum pattern_match_result default_match,
          int progress_nr);

/* Whole directory matching */
static int clear_ce_flags_dir(struct index_state *istate,
            struct cache_entry **cache, int nr,
            struct strbuf *prefix,
            char *basename,
            int select_mask, int clear_mask,
            struct pattern_list *pl,
            enum pattern_match_result default_match,
            int progress_nr)
{
  struct cache_entry **cache_end;
  int dtype = DT_DIR;
  int rc;
  enum pattern_match_result ret, orig_ret;
  orig_ret = path_matches_pattern_list(prefix->buf, prefix->len,
               basename, &dtype, pl, istate);

  strbuf_addch(prefix, '/');

  /* If undecided, use matching result of parent dir in defval */
  if (orig_ret == UNDECIDED)
    ret = default_match;
  else
    ret = orig_ret;

  for (cache_end = cache; cache_end != cache + nr; cache_end++) {
    struct cache_entry *ce = *cache_end;
    if (strncmp(ce->name, prefix->buf, prefix->len))
      break;
  }

  if (pl->use_cone_patterns && orig_ret == MATCHED_RECURSIVE) {
    struct cache_entry **ce = cache;
    rc = cache_end - cache;

    while (ce < cache_end) {
      (*ce)->ce_flags &= ~clear_mask;
      ce++;
    }
  } else if (pl->use_cone_patterns && orig_ret == NOT_MATCHED) {
    rc = cache_end - cache;
  } else {
    rc = clear_ce_flags_1(istate, cache, cache_end - cache,
              prefix,
              select_mask, clear_mask,
              pl, ret,
              progress_nr);
  }

  strbuf_setlen(prefix, prefix->len - 1);
  return rc;
}

/*
 * Traverse the index, find every entry that matches according to
 * o->pl. Do "ce_flags &= ~clear_mask" on those entries. Return the
 * number of traversed entries.
 *
 * If select_mask is non-zero, only entries whose ce_flags has on of
 * those bits enabled are traversed.
 *
 * cache  : pointer to an index entry
 * prefix_len : an offset to its path
 *
 * The current path ("prefix") including the trailing '/' is
 *   cache[0]->name[0..(prefix_len-1)]
 * Top level path has prefix_len zero.
 */
static int clear_ce_flags_1(struct index_state *istate,
          struct cache_entry **cache, int nr,
          struct strbuf *prefix,
          int select_mask, int clear_mask,
          struct pattern_list *pl,
          enum pattern_match_result default_match,
          int progress_nr)
{
  struct cache_entry **cache_end = nr ? cache + nr : cache;

  /*
   * Process all entries that have the given prefix and meet
   * select_mask condition
   */
  while(cache != cache_end) {
    struct cache_entry *ce = *cache;
    const char *name, *slash;
    int len, dtype;
    enum pattern_match_result ret;

    display_progress(istate->progress, progress_nr);

    if (select_mask && !(ce->ce_flags & select_mask)) {
      cache++;
      progress_nr++;
      continue;
    }

    if (prefix->len && strncmp(ce->name, prefix->buf, prefix->len))
      break;

    name = ce->name + prefix->len;
    slash = strchr(name, '/');

    /* If it's a directory, try whole directory match first */
    if (slash) {
      int processed;

      len = slash - name;
      strbuf_add(prefix, name, len);

      processed = clear_ce_flags_dir(istate, cache, cache_end - cache,
                   prefix,
                   prefix->buf + prefix->len - len,
                   select_mask, clear_mask,
                   pl, default_match,
                   progress_nr);

      /* clear_c_f_dir eats a whole dir already? */
      if (processed) {
        cache += processed;
        progress_nr += processed;
        strbuf_setlen(prefix, prefix->len - len);
        continue;
      }

      strbuf_addch(prefix, '/');
      processed = clear_ce_flags_1(istate, cache, cache_end - cache,
                 prefix,
                 select_mask, clear_mask, pl,
                 default_match, progress_nr);

      cache += processed;
      progress_nr += processed;

      strbuf_setlen(prefix, prefix->len - len - 1);
      continue;
    }

    /* Non-directory */
    dtype = ce_to_dtype(ce);
    ret = path_matches_pattern_list(ce->name,
            ce_namelen(ce),
            name, &dtype, pl, istate);
    if (ret == UNDECIDED)
      ret = default_match;
    if (ret == MATCHED || ret == MATCHED_RECURSIVE)
      ce->ce_flags &= ~clear_mask;
    cache++;
    progress_nr++;
  }

  display_progress(istate->progress, progress_nr);
  return nr - (cache_end - cache);
}

static int clear_ce_flags(struct index_state *istate,
        int select_mask, int clear_mask,
        struct pattern_list *pl,
        int show_progress)
{
  static struct strbuf prefix = STRBUF_INIT;
  char label[100];
  int rval;

  strbuf_reset(&prefix);
  if (show_progress)
    istate->progress = start_delayed_progress(
          _("Updating index flags"),
          istate->cache_nr);

  xsnprintf(label, sizeof(label), "clear_ce_flags(0x%08lx,0x%08lx)",
      (unsigned long)select_mask, (unsigned long)clear_mask);
  trace2_region_enter("unpack_trees", label, the_repository);
  rval = clear_ce_flags_1(istate,
        istate->cache,
        istate->cache_nr,
        &prefix,
        select_mask, clear_mask,
        pl, 0, 0);
  trace2_region_leave("unpack_trees", label, the_repository);

  stop_progress(&istate->progress);
  return rval;
}

/*
 * Set/Clear CE_NEW_SKIP_WORKTREE according to $GIT_DIR/info/sparse-checkout
 */
static void mark_new_skip_worktree(struct pattern_list *pl,
           struct index_state *istate,
           int select_flag, int skip_wt_flag,
           int show_progress)
{
  int i;

  /*
   * 1. Pretend the narrowest worktree: only unmerged entries
   * are checked out
   */
  for (i = 0; i < istate->cache_nr; i++) {
    struct cache_entry *ce = istate->cache[i];

    if (select_flag && !(ce->ce_flags & select_flag))
      continue;

    if (!ce_stage(ce) && !(ce->ce_flags & CE_CONFLICTED))
      ce->ce_flags |= skip_wt_flag;
    else
      ce->ce_flags &= ~skip_wt_flag;
  }

  /*
   * 2. Widen worktree according to sparse-checkout file.
   * Matched entries will have skip_wt_flag cleared (i.e. "in")
   */
  clear_ce_flags(istate, select_flag, skip_wt_flag, pl, show_progress);
}

static void populate_from_existing_patterns(struct unpack_trees_options *o,
              struct pattern_list *pl)
{
  if (get_sparse_checkout_patterns(pl) < 0)
    o->skip_sparse_checkout = 1;
  else
    o->internal.pl = pl;
}

static void update_sparsity_for_prefix(const char *prefix,
               struct index_state *istate)
{
  int prefix_len = strlen(prefix);
  struct strbuf ce_prefix = STRBUF_INIT;

  if (!istate->sparse_index)
    return;

  while (prefix_len > 0 && prefix[prefix_len - 1] == '/')
    prefix_len--;

  if (prefix_len <= 0)
    BUG("Invalid prefix passed to update_sparsity_for_prefix");

  strbuf_grow(&ce_prefix, prefix_len + 1);
  strbuf_add(&ce_prefix, prefix, prefix_len);
  strbuf_addch(&ce_prefix, '/');

  /*
   * If the prefix points to a sparse directory or a path inside a sparse
   * directory, the index should be expanded. This is accomplished in one
   * of two ways:
   * - if the prefix is inside a sparse directory, it will be expanded by
   *   the 'ensure_full_index(...)' call in 'index_name_pos(...)'.
   * - if the prefix matches an existing sparse directory entry,
   *   'index_name_pos(...)' will return its index position, triggering
   *   the 'ensure_full_index(...)' below.
   */
  if (!path_in_cone_mode_sparse_checkout(ce_prefix.buf, istate) &&
      index_name_pos(istate, ce_prefix.buf, ce_prefix.len) >= 0)
    ensure_full_index(istate);

  strbuf_release(&ce_prefix);
}

static int verify_absent(const struct cache_entry *,
       enum unpack_trees_error_types,
       struct unpack_trees_options *);
/*
 * N-way merge "len" trees.  Returns 0 on success, -1 on failure to manipulate the
 * resulting index, -2 on failure to reflect the changes to the work tree.
 *
 * CE_ADDED, CE_UNPACKED and CE_NEW_SKIP_WORKTREE are used internally
 */
int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options *o)
{
  struct repository *repo = the_repository;
  int i, ret;
  static struct cache_entry *dfc;
  struct pattern_list pl;
  int free_pattern_list = 0;
  struct dir_struct dir = DIR_INIT;

  if (o->reset == UNPACK_RESET_INVALID)
    BUG("o->reset had a value of 1; should be UNPACK_TREES_*_UNTRACKED");

  if (len > MAX_UNPACK_TREES)
    die("unpack_trees takes at most %d trees", MAX_UNPACK_TREES);
  if (o->internal.dir)
    BUG("o->internal.dir is for internal use only");
  if (o->internal.pl)
    BUG("o->internal.pl is for internal use only");
  if (o->df_conflict_entry)
    BUG("o->df_conflict_entry is an output only field");

  trace_performance_enter();
  trace2_region_enter("unpack_trees", "unpack_trees", the_repository);

  prepare_repo_settings(repo);
  if (repo->settings.command_requires_full_index) {
    ensure_full_index(o->src_index);
    if (o->dst_index)
      ensure_full_index(o->dst_index);
  }

  if (o->reset == UNPACK_RESET_OVERWRITE_UNTRACKED &&
      o->preserve_ignored)
    BUG("UNPACK_RESET_OVERWRITE_UNTRACKED incompatible with preserved ignored files");

  if (!o->preserve_ignored) {
    o->internal.dir = &dir;
    o->internal.dir->flags |= DIR_SHOW_IGNORED;
    setup_standard_excludes(o->internal.dir);
  }

  if (o->prefix)
    update_sparsity_for_prefix(o->prefix, o->src_index);

  if (!core_apply_sparse_checkout || !o->update)
    o->skip_sparse_checkout = 1;
  if (!o->skip_sparse_checkout) {
    memset(&pl, 0, sizeof(pl));
    free_pattern_list = 1;
    populate_from_existing_patterns(o, &pl);
  }

  index_state_init(&o->internal.result, o->src_index->repo);
  o->internal.result.initialized = 1;
  o->internal.result.timestamp.sec = o->src_index->timestamp.sec;
  o->internal.result.timestamp.nsec = o->src_index->timestamp.nsec;
  o->internal.result.version = o->src_index->version;
  if (!o->src_index->split_index) {
    o->internal.result.split_index = NULL;
  } else if (o->src_index == o->dst_index) {
    /*
     * o->dst_index (and thus o->src_index) will be discarded
     * and overwritten with o->internal.result at the end of
     * this function, so just use src_index's split_index to
     * avoid having to create a new one.
     */
    o->internal.result.split_index = o->src_index->split_index;
    if (o->src_index->cache_changed & SPLIT_INDEX_ORDERED)
      o->internal.result.cache_changed |= SPLIT_INDEX_ORDERED;
    o->internal.result.split_index->refcount++;
  } else {
    o->internal.result.split_index =
      init_split_index(&o->internal.result);
  }
  oidcpy(&o->internal.result.oid, &o->src_index->oid);
  o->internal.merge_size = len;
  mark_all_ce_unused(o->src_index);

  o->internal.result.fsmonitor_last_update =
    xstrdup_or_null(o->src_index->fsmonitor_last_update);
  o->internal.result.fsmonitor_has_run_once = o->src_index->fsmonitor_has_run_once;

  if (!o->src_index->initialized &&
      !repo->settings.command_requires_full_index &&
      is_sparse_index_allowed(&o->internal.result, 0))
    o->internal.result.sparse_index = 1;

  /*
   * Sparse checkout loop #1: set NEW_SKIP_WORKTREE on existing entries
   */
  if (!o->skip_sparse_checkout)
    mark_new_skip_worktree(o->internal.pl, o->src_index, 0,
               CE_NEW_SKIP_WORKTREE, o->verbose_update);

  if (!dfc)
    dfc = xcalloc(1, cache_entry_size(0));
  o->df_conflict_entry = dfc;

  if (len) {
    const char *prefix = o->prefix ? o->prefix : "";
    struct traverse_info info;

    setup_traverse_info(&info, prefix);
    info.fn = unpack_callback;
    info.data = o;
    info.show_all_errors = o->internal.show_all_errors;
    info.pathspec = o->pathspec;

    if (o->prefix) {
      /*
       * Unpack existing index entries that sort before the
       * prefix the tree is spliced into.  Note that o->merge
       * is always true in this case.
       */
      while (1) {
        struct cache_entry *ce = next_cache_entry(o);
        if (!ce)
          break;
        if (ce_in_traverse_path(ce, &info))
          break;
        if (unpack_index_entry(ce, o) < 0)
          goto return_failed;
      }
    }

    trace_performance_enter();
    trace2_region_enter("unpack_trees", "traverse_trees", the_repository);
    ret = traverse_trees(o->src_index, len, t, &info);
    trace2_region_leave("unpack_trees", "traverse_trees", the_repository);
    trace_performance_leave("traverse_trees");
    if (ret < 0)
      goto return_failed;
  }

  /* Any left-over entries in the index? */
  if (o->merge) {
    while (1) {
      struct cache_entry *ce = next_cache_entry(o);
      if (!ce)
        break;
      if (unpack_index_entry(ce, o) < 0)
        goto return_failed;
    }
  }
  mark_all_ce_unused(o->src_index);

  if (o->trivial_merges_only && o->internal.nontrivial_merge) {
    ret = unpack_failed(o, "Merge requires file-level merging");
    goto done;
  }

  if (!o->skip_sparse_checkout) {
    /*
     * Sparse checkout loop #2: set NEW_SKIP_WORKTREE on entries not in loop #1
     * If they will have NEW_SKIP_WORKTREE, also set CE_SKIP_WORKTREE
     * so apply_sparse_checkout() won't attempt to remove it from worktree
     */
    mark_new_skip_worktree(o->internal.pl, &o->internal.result,
               CE_ADDED, CE_SKIP_WORKTREE | CE_NEW_SKIP_WORKTREE,
               o->verbose_update);

    ret = 0;
    for (i = 0; i < o->internal.result.cache_nr; i++) {
      struct cache_entry *ce = o->internal.result.cache[i];

      /*
       * Entries marked with CE_ADDED in merged_entry() do not have
       * verify_absent() check (the check is effectively disabled
       * because CE_NEW_SKIP_WORKTREE is set unconditionally).
       *
       * Do the real check now because we have had
       * correct CE_NEW_SKIP_WORKTREE
       */
      if (ce->ce_flags & CE_ADDED &&
          verify_absent(ce, WARNING_SPARSE_ORPHANED_NOT_OVERWRITTEN, o))
        ret = 1;

      if (apply_sparse_checkout(&o->internal.result, ce, o))
        ret = 1;
    }
    if (ret == 1) {
      /*
       * Inability to sparsify or de-sparsify individual
       * paths is not an error, but just a warning.
       */
      if (o->internal.show_all_errors)
        display_warning_msgs(o);
      ret = 0;
    }
  }

  ret = check_updates(o, &o->internal.result) ? (-2) : 0;
  if (o->dst_index) {
    move_index_extensions(&o->internal.result, o->src_index);
    if (!ret) {
      if (git_env_bool("GIT_TEST_CHECK_CACHE_TREE", 0))
        cache_tree_verify(the_repository,
              &o->internal.result);
      if (!o->skip_cache_tree_update &&
          !cache_tree_fully_valid(o->internal.result.cache_tree))
        cache_tree_update(&o->internal.result,
              WRITE_TREE_SILENT |
              WRITE_TREE_REPAIR);
    }

    o->internal.result.updated_workdir = 1;
    discard_index(o->dst_index);
    *o->dst_index = o->internal.result;
    memset(&o->internal.result, 0, sizeof(o->internal.result));
  } else {
    discard_index(&o->internal.result);
  }
  o->src_index = NULL;

done:
  if (free_pattern_list)
    clear_pattern_list(&pl);
  if (o->internal.dir) {
    dir_clear(o->internal.dir);
    o->internal.dir = NULL;
  }
  trace2_region_leave("unpack_trees", "unpack_trees", the_repository);
  trace_performance_leave("unpack_trees");
  return ret;

return_failed:
  if (o->internal.show_all_errors)
    display_error_msgs(o);
  mark_all_ce_unused(o->src_index);
  ret = unpack_failed(o, NULL);
  if (o->exiting_early)
    ret = 0;
  goto done;
}

/*
 * Update SKIP_WORKTREE bits according to sparsity patterns, and update
 * working directory to match.
 *
 * CE_NEW_SKIP_WORKTREE is used internally.
 */
enum update_sparsity_result update_sparsity(struct unpack_trees_options *o,
              struct pattern_list *pl)
{
  enum update_sparsity_result ret = UPDATE_SPARSITY_SUCCESS;
  int i;
  unsigned old_show_all_errors;
  int free_pattern_list = 0;

  old_show_all_errors = o->internal.show_all_errors;
  o->internal.show_all_errors = 1;
  index_state_init(&o->internal.result, o->src_index->repo);

  /* Sanity checks */
  if (!o->update || o->index_only || o->skip_sparse_checkout)
    BUG("update_sparsity() is for reflecting sparsity patterns in working directory");
  if (o->src_index != o->dst_index || o->fn)
    BUG("update_sparsity() called wrong");

  trace_performance_enter();

  /* If we weren't given patterns, use the recorded ones */
  if (!pl) {
    free_pattern_list = 1;
    pl = xcalloc(1, sizeof(*pl));
    populate_from_existing_patterns(o, pl);
  }
  o->internal.pl = pl;

  /* Expand sparse directories as needed */
  expand_index(o->src_index, o->internal.pl);

  /* Set NEW_SKIP_WORKTREE on existing entries. */
  mark_all_ce_unused(o->src_index);
  mark_new_skip_worktree(o->internal.pl, o->src_index, 0,
             CE_NEW_SKIP_WORKTREE, o->verbose_update);

  /* Then loop over entries and update/remove as needed */
  ret = UPDATE_SPARSITY_SUCCESS;
  for (i = 0; i < o->src_index->cache_nr; i++) {
    struct cache_entry *ce = o->src_index->cache[i];


    if (ce_stage(ce)) {
      /* -1 because for loop will increment by 1 */
      i += warn_conflicted_path(o->src_index, i, o) - 1;
      ret = UPDATE_SPARSITY_WARNINGS;
      continue;
    }

    if (apply_sparse_checkout(o->src_index, ce, o))
      ret = UPDATE_SPARSITY_WARNINGS;
  }

  if (check_updates(o, o->src_index))
    ret = UPDATE_SPARSITY_WORKTREE_UPDATE_FAILURES;

  display_warning_msgs(o);
  o->internal.show_all_errors = old_show_all_errors;
  if (free_pattern_list) {
    clear_pattern_list(pl);
    free(pl);
    o->internal.pl = NULL;
  }
  trace_performance_leave("update_sparsity");
  return ret;
}

/* Here come the merge functions */

static int reject_merge(const struct cache_entry *ce,
      struct unpack_trees_options *o)
{
  return add_rejected_path(o, ERROR_WOULD_OVERWRITE, ce->name);
}

static int same(const struct cache_entry *a, const struct cache_entry *b)
{
  if (!!a != !!b)
    return 0;
  if (!a && !b)
    return 1;
  if ((a->ce_flags | b->ce_flags) & CE_CONFLICTED)
    return 0;
  return a->ce_mode == b->ce_mode &&
         oideq(&a->oid, &b->oid);
}


/*
 * When a CE gets turned into an unmerged entry, we
 * want it to be up-to-date
 */
static int verify_uptodate_1(const struct cache_entry *ce,
           struct unpack_trees_options *o,
           enum unpack_trees_error_types error_type)
{
  struct stat st;

  if (o->index_only)
    return 0;

  /*
   * CE_VALID and CE_SKIP_WORKTREE cheat, we better check again
   * if this entry is truly up-to-date because this file may be
   * overwritten.
   */
  if ((ce->ce_flags & CE_VALID) || ce_skip_worktree(ce))
    ; /* keep checking */
  else if (o->reset || ce_uptodate(ce))
    return 0;

  if (!lstat(ce->name, &st)) {
    int flags = CE_MATCH_IGNORE_VALID|CE_MATCH_IGNORE_SKIP_WORKTREE;
    unsigned changed = ie_match_stat(o->src_index, ce, &st, flags);

    if (submodule_from_ce(ce)) {
      int r = check_submodule_move_head(ce,
        "HEAD", oid_to_hex(&ce->oid), o);
      if (r)
        return add_rejected_path(o, error_type, ce->name);
      return 0;
    }

    if (!changed)
      return 0;
    /*
     * Historic default policy was to allow submodule to be out
     * of sync wrt the superproject index. If the submodule was
     * not considered interesting above, we don't care here.
     */
    if (S_ISGITLINK(ce->ce_mode))
      return 0;

    errno = 0;
  }
  if (errno == ENOENT)
    return 0;
  return add_rejected_path(o, error_type, ce->name);
}

int verify_uptodate(const struct cache_entry *ce,
        struct unpack_trees_options *o)
{
  if (!o->skip_sparse_checkout &&
      (ce->ce_flags & CE_SKIP_WORKTREE) &&
      (ce->ce_flags & CE_NEW_SKIP_WORKTREE))
    return 0;
  return verify_uptodate_1(ce, o, ERROR_NOT_UPTODATE_FILE);
}

static int verify_uptodate_sparse(const struct cache_entry *ce,
          struct unpack_trees_options *o)
{
  return verify_uptodate_1(ce, o, WARNING_SPARSE_NOT_UPTODATE_FILE);
}

/*
 * TODO: We should actually invalidate o->internal.result, not src_index [1].
 * But since cache tree and untracked cache both are not copied to
 * o->internal.result until unpacking is complete, we invalidate them on
 * src_index instead with the assumption that they will be copied to
 * dst_index at the end.
 *
 * [1] src_index->cache_tree is also used in unpack_callback() so if
 * we invalidate o->internal.result, we need to update it to use
 * o->internal.result.cache_tree as well.
 */
static void invalidate_ce_path(const struct cache_entry *ce,
             struct unpack_trees_options *o)
{
  if (!ce)
    return;
  cache_tree_invalidate_path(o->src_index, ce->name);
  untracked_cache_invalidate_path(o->src_index, ce->name, 1);
}

/*
 * Check that checking out ce->sha1 in subdir ce->name is not
 * going to overwrite any working files.
 */
static int verify_clean_submodule(const char *old_sha1,
          const struct cache_entry *ce,
          struct unpack_trees_options *o)
{
  if (!submodule_from_ce(ce))
    return 0;

  return check_submodule_move_head(ce, old_sha1,
           oid_to_hex(&ce->oid), o);
}

static int verify_clean_subdirectory(const struct cache_entry *ce,
             struct unpack_trees_options *o)
{
  /*
   * we are about to extract "ce->name"; we would not want to lose
   * anything in the existing directory there.
   */
  int namelen;
  int i;
  struct dir_struct d;
  char *pathbuf;
  int cnt = 0;

  if (S_ISGITLINK(ce->ce_mode)) {
    struct object_id oid;
    int sub_head = repo_resolve_gitlink_ref(the_repository, ce->name,
              "HEAD", &oid);
    /*
     * If we are not going to update the submodule, then
     * we don't care.
     */
    if (!sub_head && oideq(&oid, &ce->oid))
      return 0;
    return verify_clean_submodule(sub_head ? NULL : oid_to_hex(&oid),
                ce, o);
  }

  /*
   * First let's make sure we do not have a local modification
   * in that directory.
   */
  namelen = ce_namelen(ce);
  for (i = locate_in_src_index(ce, o);
       i < o->src_index->cache_nr;
       i++) {
    struct cache_entry *ce2 = o->src_index->cache[i];
    int len = ce_namelen(ce2);
    if (len < namelen ||
        strncmp(ce->name, ce2->name, namelen) ||
        ce2->name[namelen] != '/')
      break;
    /*
     * ce2->name is an entry in the subdirectory to be
     * removed.
     */
    if (!ce_stage(ce2)) {
      if (verify_uptodate(ce2, o))
        return -1;
      add_entry(o, ce2, CE_REMOVE, 0);
      invalidate_ce_path(ce, o);
      mark_ce_used(ce2, o);
    }
    cnt++;
  }

  /* Do not lose a locally present file that is not ignored. */
  pathbuf = xstrfmt("%.*s/", namelen, ce->name);

  memset(&d, 0, sizeof(d));
  if (o->internal.dir)
    setup_standard_excludes(&d);
  i = read_directory(&d, o->src_index, pathbuf, namelen+1, NULL);
  dir_clear(&d);
  free(pathbuf);
  if (i)
    return add_rejected_path(o, ERROR_NOT_UPTODATE_DIR, ce->name);

  /* Do not lose startup_info->original_cwd */
  if (startup_info->original_cwd &&
      !strcmp(startup_info->original_cwd, ce->name))
    return add_rejected_path(o, ERROR_CWD_IN_THE_WAY, ce->name);

  return cnt;
}

/*
 * This gets called when there was no index entry for the tree entry 'dst',
 * but we found a file in the working tree that 'lstat()' said was fine,
 * and we're on a case-insensitive filesystem.
 *
 * See if we can find a case-insensitive match in the index that also
 * matches the stat information, and assume it's that other file!
 */
static int icase_exists(struct unpack_trees_options *o, const char *name, int len, struct stat *st)
{
  const struct cache_entry *src;

  src = index_file_exists(o->src_index, name, len, 1);
  return src && !ie_match_stat(o->src_index, src, st, CE_MATCH_IGNORE_VALID|CE_MATCH_IGNORE_SKIP_WORKTREE);
}

enum absent_checking_type {
  COMPLETELY_ABSENT,
  ABSENT_ANY_DIRECTORY
};

static int check_ok_to_remove(const char *name, int len, int dtype,
            const struct cache_entry *ce, struct stat *st,
            enum unpack_trees_error_types error_type,
            enum absent_checking_type absent_type,
            struct unpack_trees_options *o)
{
  const struct cache_entry *result;

  /*
   * It may be that the 'lstat()' succeeded even though
   * target 'ce' was absent, because there is an old
   * entry that is different only in case..
   *
   * Ignore that lstat() if it matches.
   */
  if (ignore_case && icase_exists(o, name, len, st))
    return 0;

  if (o->internal.dir &&
      is_excluded(o->internal.dir, o->src_index, name, &dtype))
    /*
     * ce->name is explicitly excluded, so it is Ok to
     * overwrite it.
     */
    return 0;
  if (S_ISDIR(st->st_mode)) {
    /*
     * We are checking out path "foo" and
     * found "foo/." in the working tree.
     * This is tricky -- if we have modified
     * files that are in "foo/" we would lose
     * them.
     */
    if (verify_clean_subdirectory(ce, o) < 0)
      return -1;
    return 0;
  }

  /* If we only care about directories, then we can remove */
  if (absent_type == ABSENT_ANY_DIRECTORY)
    return 0;

  /*
   * The previous round may already have decided to
   * delete this path, which is in a subdirectory that
   * is being replaced with a blob.
   */
  result = index_file_exists(&o->internal.result, name, len, 0);
  if (result) {
    if (result->ce_flags & CE_REMOVE)
      return 0;
  }

  return add_rejected_path(o, error_type, name);
}

/*
 * We do not want to remove or overwrite a working tree file that
 * is not tracked, unless it is ignored.
 */
static int verify_absent_1(const struct cache_entry *ce,
         enum unpack_trees_error_types error_type,
         enum absent_checking_type absent_type,
         struct unpack_trees_options *o)
{
  int len;
  struct stat st;

  if (o->index_only || !o->update)
    return 0;

  if (o->reset == UNPACK_RESET_OVERWRITE_UNTRACKED) {
    /* Avoid nuking startup_info->original_cwd... */
    if (startup_info->original_cwd &&
        !strcmp(startup_info->original_cwd, ce->name))
      return add_rejected_path(o, ERROR_CWD_IN_THE_WAY,
             ce->name);
    /* ...but nuke anything else. */
    return 0;
  }

  len = check_leading_path(ce->name, ce_namelen(ce), 0);
  if (!len)
    return 0;
  else if (len > 0) {
    char *path;
    int ret;

    path = xmemdupz(ce->name, len);
    if (lstat(path, &st))
      ret = error_errno("cannot stat '%s'", path);
    else {
      if (submodule_from_ce(ce))
        ret = check_submodule_move_head(ce,
                oid_to_hex(&ce->oid),
                NULL, o);
      else
        ret = check_ok_to_remove(path, len, DT_UNKNOWN, NULL,
               &st, error_type,
               absent_type, o);
    }
    free(path);
    return ret;
  } else if (lstat(ce->name, &st)) {
    if (errno != ENOENT)
      return error_errno("cannot stat '%s'", ce->name);
    return 0;
  } else {
    if (submodule_from_ce(ce))
      return check_submodule_move_head(ce, oid_to_hex(&ce->oid),
               NULL, o);

    return check_ok_to_remove(ce->name, ce_namelen(ce),
            ce_to_dtype(ce), ce, &st,
            error_type, absent_type, o);
  }
}

static int verify_absent(const struct cache_entry *ce,
       enum unpack_trees_error_types error_type,
       struct unpack_trees_options *o)
{
  if (!o->skip_sparse_checkout && (ce->ce_flags & CE_NEW_SKIP_WORKTREE))
    return 0;
  return verify_absent_1(ce, error_type, COMPLETELY_ABSENT, o);
}

static int verify_absent_if_directory(const struct cache_entry *ce,
              enum unpack_trees_error_types error_type,
              struct unpack_trees_options *o)
{
  if (!o->skip_sparse_checkout && (ce->ce_flags & CE_NEW_SKIP_WORKTREE))
    return 0;
  return verify_absent_1(ce, error_type, ABSENT_ANY_DIRECTORY, o);
}

static int verify_absent_sparse(const struct cache_entry *ce,
        enum unpack_trees_error_types error_type,
        struct unpack_trees_options *o)
{
  return verify_absent_1(ce, error_type, COMPLETELY_ABSENT, o);
}

static int merged_entry(const struct cache_entry *ce,
      const struct cache_entry *old,
      struct unpack_trees_options *o)
{
  int update = CE_UPDATE;
  struct cache_entry *merge = dup_cache_entry(ce, &o->internal.result);

  if (!old) {
    /*
     * New index entries. In sparse checkout, the following
     * verify_absent() will be delayed until after
     * traverse_trees() finishes in unpack_trees(), then:
     *
     *  - CE_NEW_SKIP_WORKTREE will be computed correctly
     *  - verify_absent() be called again, this time with
     *    correct CE_NEW_SKIP_WORKTREE
     *
     * verify_absent() call here does nothing in sparse
     * checkout (i.e. o->skip_sparse_checkout == 0)
     */
    update |= CE_ADDED;
    merge->ce_flags |= CE_NEW_SKIP_WORKTREE;

    if (verify_absent(merge,
          ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN, o)) {
      discard_cache_entry(merge);
      return -1;
    }
    invalidate_ce_path(merge, o);

    if (submodule_from_ce(ce) && file_exists(ce->name)) {
      int ret = check_submodule_move_head(ce, NULL,
                  oid_to_hex(&ce->oid),
                  o);
      if (ret)
        return ret;
    }

  } else if (!(old->ce_flags & CE_CONFLICTED)) {
    /*
     * See if we can re-use the old CE directly?
     * That way we get the uptodate stat info.
     *
     * This also removes the UPDATE flag on a match; otherwise
     * we will end up overwriting local changes in the work tree.
     */
    if (same(old, merge)) {
      copy_cache_entry(merge, old);
      update = 0;
    } else {
      if (verify_uptodate(old, o)) {
        discard_cache_entry(merge);
        return -1;
      }
      /* Migrate old flags over */
      update |= old->ce_flags & (CE_SKIP_WORKTREE | CE_NEW_SKIP_WORKTREE);
      invalidate_ce_path(old, o);
    }

    if (submodule_from_ce(ce) && file_exists(ce->name)) {
      int ret = check_submodule_move_head(ce, oid_to_hex(&old->oid),
                  oid_to_hex(&ce->oid),
                  o);
      if (ret)
        return ret;
    }
  } else {
    /*
     * Previously unmerged entry left as an existence
     * marker by read_index_unmerged();
     */
    if (verify_absent_if_directory(merge,
          ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN, o)) {
      discard_cache_entry(merge);
      return -1;
    }

    invalidate_ce_path(old, o);
  }

  if (do_add_entry(o, merge, update, CE_STAGEMASK) < 0)
    return -1;
  return 1;
}

static int merged_sparse_dir(const struct cache_entry * const *src, int n,
           struct unpack_trees_options *o)
{
  struct tree_desc t[MAX_UNPACK_TREES + 1];
  void * tree_bufs[MAX_UNPACK_TREES + 1];
  struct traverse_info info;
  int i, ret;

  /*
   * Create the tree traversal information for traversing into *only* the
   * sparse directory.
   */
  setup_traverse_info(&info, src[0]->name);
  info.fn = unpack_sparse_callback;
  info.data = o;
  info.show_all_errors = o->internal.show_all_errors;
  info.pathspec = o->pathspec;

  /* Get the tree descriptors of the sparse directory in each of the merging trees */
  for (i = 0; i < n; i++)
    tree_bufs[i] = fill_tree_descriptor(o->src_index->repo, &t[i],
                src[i] && !is_null_oid(&src[i]->oid) ? &src[i]->oid : NULL);

  ret = traverse_trees(o->src_index, n, t, &info);

  for (i = 0; i < n; i++)
    free(tree_bufs[i]);

  return ret;
}

static int deleted_entry(const struct cache_entry *ce,
       const struct cache_entry *old,
       struct unpack_trees_options *o)
{
  /* Did it exist in the index? */
  if (!old) {
    if (verify_absent(ce, ERROR_WOULD_LOSE_UNTRACKED_REMOVED, o))
      return -1;
    return 0;
  } else if (verify_absent_if_directory(ce, ERROR_WOULD_LOSE_UNTRACKED_REMOVED, o)) {
    return -1;
  }

  if (!(old->ce_flags & CE_CONFLICTED) && verify_uptodate(old, o))
    return -1;
  add_entry(o, ce, CE_REMOVE, 0);
  invalidate_ce_path(ce, o);
  return 1;
}

static int keep_entry(const struct cache_entry *ce,
          struct unpack_trees_options *o)
{
  add_entry(o, ce, 0, 0);
  if (ce_stage(ce))
    invalidate_ce_path(ce, o);
  return 1;
}

#if DBRT_DEBUG
static void show_stage_entry(FILE *o,
           const char *label, const struct cache_entry *ce)
{
  if (!ce)
    fprintf(o, "%s (missing)\n", label);
  else
    fprintf(o, "%s%06o %s %d\t%s\n",
      label,
      ce->ce_mode,
      oid_to_hex(&ce->oid),
      ce_stage(ce),
      ce->name);
}
#endif

int threeway_merge(const struct cache_entry * const *stages,
       struct unpack_trees_options *o)
{
  const struct cache_entry *index;
  const struct cache_entry *head;
  const struct cache_entry *remote = stages[o->head_idx + 1];
  int count;
  int head_match = 0;
  int remote_match = 0;

  int df_conflict_head = 0;
  int df_conflict_remote = 0;

  int any_anc_missing = 0;
  int no_anc_exists = 1;
  int i;

  for (i = 1; i < o->head_idx; i++) {
    if (!stages[i] || stages[i] == o->df_conflict_entry)
      any_anc_missing = 1;
    else
      no_anc_exists = 0;
  }

  index = stages[0];
  head = stages[o->head_idx];

  if (head == o->df_conflict_entry) {
    df_conflict_head = 1;
    head = NULL;
  }

  if (remote == o->df_conflict_entry) {
    df_conflict_remote = 1;
    remote = NULL;
  }

  /*
   * First, if there's a #16 situation, note that to prevent #13
   * and #14.
   */
  if (!same(remote, head)) {
    for (i = 1; i < o->head_idx; i++) {
      if (same(stages[i], head)) {
        head_match = i;
      }
      if (same(stages[i], remote)) {
        remote_match = i;
      }
    }
  }

  /*
   * We start with cases where the index is allowed to match
   * something other than the head: #14(ALT) and #2ALT, where it
   * is permitted to match the result instead.
   */
  /* #14, #14ALT, #2ALT */
  if (remote && !df_conflict_head && head_match && !remote_match) {
    if (index && !same(index, remote) && !same(index, head)) {
      if (S_ISSPARSEDIR(index->ce_mode))
        return merged_sparse_dir(stages, 4, o);
      else
        return reject_merge(index, o);
    }
    return merged_entry(remote, index, o);
  }
  /*
   * If we have an entry in the index cache, then we want to
   * make sure that it matches head.
   */
  if (index && !same(index, head)) {
    if (S_ISSPARSEDIR(index->ce_mode))
      return merged_sparse_dir(stages, 4, o);
    else
      return reject_merge(index, o);
  }

  if (head) {
    /* #5ALT, #15 */
    if (same(head, remote))
      return merged_entry(head, index, o);
    /* #13, #3ALT */
    if (!df_conflict_remote && remote_match && !head_match)
      return merged_entry(head, index, o);
  }

  /* #1 */
  if (!head && !remote && any_anc_missing)
    return 0;

  /*
   * Under the "aggressive" rule, we resolve mostly trivial
   * cases that we historically had git-merge-one-file resolve.
   */
  if (o->aggressive) {
    int head_deleted = !head;
    int remote_deleted = !remote;
    const struct cache_entry *ce = NULL;

    if (index)
      ce = index;
    else if (head)
      ce = head;
    else if (remote)
      ce = remote;
    else {
      for (i = 1; i < o->head_idx; i++) {
        if (stages[i] && stages[i] != o->df_conflict_entry) {
          ce = stages[i];
          break;
        }
      }
    }

    /*
     * Deleted in both.
     * Deleted in one and unchanged in the other.
     */
    if ((head_deleted && remote_deleted) ||
        (head_deleted && remote && remote_match) ||
        (remote_deleted && head && head_match)) {
      if (index)
        return deleted_entry(index, index, o);
      if (ce && !head_deleted) {
        if (verify_absent(ce, ERROR_WOULD_LOSE_UNTRACKED_REMOVED, o))
          return -1;
      }
      return 0;
    }
    /*
     * Added in both, identically.
     */
    if (no_anc_exists && head && remote && same(head, remote))
      return merged_entry(head, index, o);

  }

  /* Handle "no merge" cases (see t/t1000-read-tree-m-3way.sh) */
  if (index) {
    /*
     * If we've reached the "no merge" cases and we're merging
     * a sparse directory, we may have an "edit/edit" conflict that
     * can be resolved by individually merging directory contents.
     */
    if (S_ISSPARSEDIR(index->ce_mode))
      return merged_sparse_dir(stages, 4, o);

    /*
     * If we're not merging a sparse directory, ensure the index is
     * up-to-date to avoid files getting overwritten with conflict
     * resolution files
     */
    if (verify_uptodate(index, o))
      return -1;
  }

  o->internal.nontrivial_merge = 1;

  /* #2, #3, #4, #6, #7, #9, #10, #11. */
  count = 0;
  if (!head_match || !remote_match) {
    for (i = 1; i < o->head_idx; i++) {
      if (stages[i] && stages[i] != o->df_conflict_entry) {
        keep_entry(stages[i], o);
        count++;
        break;
      }
    }
  }
#if DBRT_DEBUG
  else {
    fprintf(stderr, "read-tree: warning #16 detected\n");
    show_stage_entry(stderr, "head   ", stages[head_match]);
    show_stage_entry(stderr, "remote ", stages[remote_match]);
  }
#endif
  if (head) { count += keep_entry(head, o); }
  if (remote) { count += keep_entry(remote, o); }
  return count;
}

/*
 * Two-way merge.
 *
 * The rule is to "carry forward" what is in the index without losing
 * information across a "fast-forward", favoring a successful merge
 * over a merge failure when it makes sense.  For details of the
 * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
 *
 */
int twoway_merge(const struct cache_entry * const *src,
     struct unpack_trees_options *o)
{
  const struct cache_entry *current = src[0];
  const struct cache_entry *oldtree = src[1];
  const struct cache_entry *newtree = src[2];

  if (o->internal.merge_size != 2)
    return error("Cannot do a twoway merge of %d trees",
           o->internal.merge_size);

  if (oldtree == o->df_conflict_entry)
    oldtree = NULL;
  if (newtree == o->df_conflict_entry)
    newtree = NULL;

  if (current) {
    if (current->ce_flags & CE_CONFLICTED) {
      if (same(oldtree, newtree) || o->reset) {
        if (!newtree)
          return deleted_entry(current, current, o);
        else
          return merged_entry(newtree, current, o);
      }
      return reject_merge(current, o);
    } else if ((!oldtree && !newtree) || /* 4 and 5 */
       (!oldtree && newtree &&
        same(current, newtree)) || /* 6 and 7 */
       (oldtree && newtree &&
        same(oldtree, newtree)) || /* 14 and 15 */
       (oldtree && newtree &&
        !same(oldtree, newtree) && /* 18 and 19 */
        same(current, newtree))) {
      return keep_entry(current, o);
    } else if (oldtree && !newtree && same(current, oldtree)) {
      /* 10 or 11 */
      return deleted_entry(oldtree, current, o);
    } else if (oldtree && newtree &&
       same(current, oldtree) && !same(current, newtree)) {
      /* 20 or 21 */
      return merged_entry(newtree, current, o);
    } else if (current && !oldtree && newtree &&
         S_ISSPARSEDIR(current->ce_mode) != S_ISSPARSEDIR(newtree->ce_mode) &&
         ce_stage(current) == 0) {
      /*
       * This case is a directory/file conflict across the sparse-index
       * boundary. When we are changing from one path to another via
       * 'git checkout', then we want to replace one entry with another
       * via merged_entry(). If there are staged changes, then we should
       * reject the merge instead.
       */
      return merged_entry(newtree, current, o);
    } else if (S_ISSPARSEDIR(current->ce_mode)) {
      /*
       * The sparse directories differ, but we don't know whether that's
       * because of two different files in the directory being modified
       * (can be trivially merged) or if there is a real file conflict.
       * Merge the sparse directory by OID to compare file-by-file.
       */
      return merged_sparse_dir(src, 3, o);
    } else
      return reject_merge(current, o);
  }
  else if (newtree) {
    if (oldtree && !o->initial_checkout) {
      /*
       * deletion of the path was staged;
       */
      if (same(oldtree, newtree))
        return 1;
      return reject_merge(oldtree, o);
    }
    return merged_entry(newtree, current, o);
  }
  return deleted_entry(oldtree, current, o);
}

/*
 * Bind merge.
 *
 * Keep the index entries at stage0, collapse stage1 but make sure
 * stage0 does not have anything there.
 */
int bind_merge(const struct cache_entry * const *src,
         struct unpack_trees_options *o)
{
  const struct cache_entry *old = src[0];
  const struct cache_entry *a = src[1];

  if (o->internal.merge_size != 1)
    return error("Cannot do a bind merge of %d trees",
           o->internal.merge_size);
  if (a && old)
    return o->quiet ? -1 :
      error(ERRORMSG(o, ERROR_BIND_OVERLAP),
            super_prefixed(a->name, o->super_prefix),
            super_prefixed(old->name, o->super_prefix));
  if (!a)
    return keep_entry(old, o);
  else
    return merged_entry(a, NULL, o);
}

/*
 * One-way merge.
 *
 * The rule is:
 * - take the stat information from stage0, take the data from stage1
 */
int oneway_merge(const struct cache_entry * const *src,
     struct unpack_trees_options *o)
{
  const struct cache_entry *old = src[0];
  const struct cache_entry *a = src[1];

  if (o->internal.merge_size != 1)
    return error("Cannot do a oneway merge of %d trees",
           o->internal.merge_size);

  if (!a || a == o->df_conflict_entry)
    return deleted_entry(old, old, o);

  if (old && same(old, a)) {
    int update = 0;
    if (o->reset && o->update && !ce_uptodate(old) && !ce_skip_worktree(old) &&
      !(old->ce_flags & CE_FSMONITOR_VALID)) {
      struct stat st;
      if (lstat(old->name, &st) ||
          ie_match_stat(o->src_index, old, &st, CE_MATCH_IGNORE_VALID|CE_MATCH_IGNORE_SKIP_WORKTREE))
        update |= CE_UPDATE;
    }
    if (o->update && S_ISGITLINK(old->ce_mode) &&
        should_update_submodules() && !verify_uptodate(old, o))
      update |= CE_UPDATE;
    add_entry(o, old, update, CE_STAGEMASK);
    return 0;
  }
  return merged_entry(a, old, o);
}

/*
 * Merge worktree and untracked entries in a stash entry.
 *
 * Ignore all index entries. Collapse remaining trees but make sure that they
 * don't have any conflicting files.
 */
int stash_worktree_untracked_merge(const struct cache_entry * const *src,
           struct unpack_trees_options *o)
{
  const struct cache_entry *worktree = src[1];
  const struct cache_entry *untracked = src[2];

  if (o->internal.merge_size != 2)
    BUG("invalid merge_size: %d", o->internal.merge_size);

  if (worktree && untracked)
    return error(_("worktree and untracked commit have duplicate entries: %s"),
           super_prefixed(worktree->name, o->super_prefix));

  return merged_entry(worktree ? worktree : untracked, NULL, o);
}

Coverage Report

Created: 2024-09-08 06:23