/src/git/sparse-index.c

Source
#define USE_THE_REPOSITORY_VARIABLE
#define DISABLE_SIGN_COMPARE_WARNINGS

#include "git-compat-util.h"
#include "environment.h"
#include "ewah/ewok.h"
#include "gettext.h"
#include "name-hash.h"
#include "read-cache-ll.h"
#include "repository.h"
#include "sparse-index.h"
#include "tree.h"
#include "pathspec.h"
#include "trace2.h"
#include "cache-tree.h"
#include "config.h"
#include "dir.h"
#include "fsmonitor-ll.h"
#include "advice.h"

/**
 * This global is used by expand_index() to determine if we should give the
 * advice for advice.sparseIndexExpanded when expanding a sparse index to a full
 * one. However, this is sometimes done on purpose, such as in the sparse-checkout
 * builtin, even when index.sparse=false. This may be disabled in
 * convert_to_sparse() or by commands that know they will lead to a full
 * expansion, but this message is not actionable.
 */
int give_advice_on_expansion = 1;
#define ADVICE_MSG \
  "The sparse index is expanding to a full index, a slow operation.\n"   \
  "Your working directory likely has contents that are outside of\n"     \
  "your sparse-checkout patterns. Use 'git sparse-checkout list' to\n"   \
  "see your sparse-checkout definition and compare it to your working\n" \
  "directory contents. Cleaning up any merge conflicts or staged\n"      \
  "changes before running 'git sparse-checkout clean' or 'git\n"         \
  "sparse-checkout reapply' may assist in this cleanup."

struct modify_index_context {
  struct index_state *write;
  struct pattern_list *pl;
};

static struct cache_entry *construct_sparse_dir_entry(
        struct index_state *istate,
        const char *sparse_dir,
        struct cache_tree *tree)
{
  struct cache_entry *de;

  de = make_cache_entry(istate, S_IFDIR, &tree->oid, sparse_dir, 0, 0);

  de->ce_flags |= CE_SKIP_WORKTREE;
  return de;
}

/*
 * Returns the number of entries "inserted" into the index.
 */
static int convert_to_sparse_rec(struct index_state *istate,
         int num_converted,
         int start, int end,
         const char *ct_path, size_t ct_pathlen,
         struct cache_tree *ct)
{
  int i, can_convert = 1;
  int start_converted = num_converted;
  struct strbuf child_path = STRBUF_INIT;

  /*
   * Is the current path outside of the sparse cone?
   * Then check if the region can be replaced by a sparse
   * directory entry (everything is sparse and merged).
   */
  if (path_in_sparse_checkout(ct_path, istate))
    can_convert = 0;

  for (i = start; can_convert && i < end; i++) {
    struct cache_entry *ce = istate->cache[i];

    if (ce_stage(ce) ||
        S_ISGITLINK(ce->ce_mode) ||
        !(ce->ce_flags & CE_SKIP_WORKTREE))
      can_convert = 0;
  }

  if (can_convert) {
    struct cache_entry *se;
    se = construct_sparse_dir_entry(istate, ct_path, ct);

    istate->cache[num_converted++] = se;
    return 1;
  }

  for (i = start; i < end; ) {
    int count, span, pos = -1;
    const char *base, *slash;
    struct cache_entry *ce = istate->cache[i];

    /*
     * Detect if this is a normal entry outside of any subtree
     * entry.
     */
    base = ce->name + ct_pathlen;
    slash = strchr(base, '/');

    if (slash)
      pos = cache_tree_subtree_pos(ct, base, slash - base);

    if (pos < 0) {
      istate->cache[num_converted++] = ce;
      i++;
      continue;
    }

    span = ct->down[pos]->cache_tree->entry_count;
    if (span < 0) {
      /* cache-tree entry is invalidated, cannot collapse. */
      istate->cache[num_converted++] = ce;
      i++;
      continue;
    }

    strbuf_setlen(&child_path, 0);
    strbuf_add(&child_path, ce->name, slash - ce->name + 1);

    count = convert_to_sparse_rec(istate,
                num_converted, i, i + span,
                child_path.buf, child_path.len,
                ct->down[pos]->cache_tree);
    num_converted += count;
    i += span;
  }

  strbuf_release(&child_path);
  return num_converted - start_converted;
}

int set_sparse_index_config(struct repository *repo, int enable)
{
  int res = repo_config_set_worktree_gently(repo,
              "index.sparse",
              enable ? "true" : "false");
  prepare_repo_settings(repo);
  repo->settings.sparse_index = enable;
  return res;
}

static int index_has_unmerged_entries(struct index_state *istate)
{
  int i;
  for (i = 0; i < istate->cache_nr; i++) {
    if (ce_stage(istate->cache[i]))
      return 1;
  }

  return 0;
}

int is_sparse_index_allowed(struct index_state *istate, int flags)
{
  struct repo_config_values *cfg = repo_config_values(the_repository);

  if (!cfg->apply_sparse_checkout || !cfg->core_sparse_checkout_cone)
    return 0;

  if (!(flags & SPARSE_INDEX_MEMORY_ONLY)) {
    int test_env;

    /*
     * The sparse index is not (yet) integrated with a split index.
     */
    if (istate->split_index || git_env_bool("GIT_TEST_SPLIT_INDEX", 0))
      return 0;
    /*
     * The GIT_TEST_SPARSE_INDEX environment variable triggers the
     * index.sparse config variable to be on.
     */
    test_env = git_env_bool("GIT_TEST_SPARSE_INDEX", -1);
    if (test_env >= 0)
      set_sparse_index_config(istate->repo, test_env);

    /*
     * Only convert to sparse if index.sparse is set.
     */
    prepare_repo_settings(istate->repo);
    if (!istate->repo->settings.sparse_index)
      return 0;
  }

  if (init_sparse_checkout_patterns(istate))
    return 0;

  /*
   * We need cone-mode patterns to use sparse-index. If a user edits
   * their sparse-checkout file manually, then we can detect during
   * parsing that they are not actually using cone-mode patterns and
   * hence we need to abort this conversion _without error_. Warnings
   * already exist in the pattern parsing to inform the user of their
   * bad patterns.
   */
  if (!istate->sparse_checkout_patterns->use_cone_patterns)
    return 0;

  return 1;
}

int convert_to_sparse(struct index_state *istate, int flags)
{
  /*
   * If the index is already sparse, empty, or otherwise
   * cannot be converted to sparse, do not convert.
   */
  if (istate->sparse_index == INDEX_COLLAPSED || !istate->cache_nr ||
      !is_sparse_index_allowed(istate, flags))
    return 0;

  /*
   * If we are purposefully collapsing a full index, then don't give
   * advice when it is expanded later.
   */
  give_advice_on_expansion = 0;

  /*
   * NEEDSWORK: If we have unmerged entries, then stay full.
   * Unmerged entries prevent the cache-tree extension from working.
   */
  if (index_has_unmerged_entries(istate))
    return 0;

  if (!cache_tree_fully_valid(istate)) {
    /* Clear and recompute the cache-tree */
    cache_tree_free(&istate->cache_tree);

    /*
     * Silently return if there is a problem with the cache tree update,
     * which might just be due to a conflict state in some entry.
     *
     * This might create new tree objects, so be sure to use
     * WRITE_TREE_MISSING_OK.
     */
    if (cache_tree_update(istate, WRITE_TREE_MISSING_OK))
      return 0;
  }

  remove_fsmonitor(istate);

  trace2_region_enter("index", "convert_to_sparse", istate->repo);
  istate->cache_nr = convert_to_sparse_rec(istate,
             0, 0, istate->cache_nr,
             "", 0, istate->cache_tree);

  /* Clear and recompute the cache-tree */
  cache_tree_free(&istate->cache_tree);
  cache_tree_update(istate, 0);

  istate->fsmonitor_has_run_once = 0;
  ewah_free(istate->fsmonitor_dirty);
  istate->fsmonitor_dirty = NULL;
  FREE_AND_NULL(istate->fsmonitor_last_update);

  istate->sparse_index = INDEX_COLLAPSED;
  trace2_region_leave("index", "convert_to_sparse", istate->repo);
  return 0;
}

static void set_index_entry(struct index_state *istate, int nr, struct cache_entry *ce)
{
  ALLOC_GROW(istate->cache, nr + 1, istate->cache_alloc);

  istate->cache[nr] = ce;
  add_name_hash(istate, ce);
}

static int add_path_to_index(const struct object_id *oid,
           struct strbuf *base, const char *path,
           unsigned int mode, void *context)
{
  struct modify_index_context *ctx = (struct modify_index_context *)context;
  struct cache_entry *ce;
  size_t len = base->len;

  if (S_ISDIR(mode)) {
    int dtype;
    size_t baselen = base->len;
    if (!ctx->pl)
      return READ_TREE_RECURSIVE;

    /*
     * Have we expanded to a point outside of the sparse-checkout?
     *
     * Artificially pad the path name with a slash "/" to
     * indicate it as a directory, and add an arbitrary file
     * name ("-") so we can consider base->buf as a file name
     * to match against the cone-mode patterns.
     *
     * If we compared just "path", then we would expand more
     * than we should. Since every file at root is always
     * included, we would expand every directory at root at
     * least one level deep instead of using sparse directory
     * entries.
     */
    strbuf_addstr(base, path);
    strbuf_add(base, "/-", 2);

    if (path_matches_pattern_list(base->buf, base->len,
                NULL, &dtype,
                ctx->pl, ctx->write)) {
      strbuf_setlen(base, baselen);
      return READ_TREE_RECURSIVE;
    }

    /*
     * The path "{base}{path}/" is a sparse directory. Create the correct
     * name for inserting the entry into the index.
     */
    strbuf_setlen(base, base->len - 1);
  } else {
    strbuf_addstr(base, path);
  }

  ce = make_cache_entry(ctx->write, mode, oid, base->buf, 0, 0);
  ce->ce_flags |= CE_SKIP_WORKTREE | CE_EXTENDED;
  set_index_entry(ctx->write, ctx->write->cache_nr++, ce);

  strbuf_setlen(base, len);
  return 0;
}

void expand_index(struct index_state *istate, struct pattern_list *pl)
{
  int i;
  struct index_state *full;
  struct strbuf base = STRBUF_INIT;
  const char *tr_region;
  struct modify_index_context ctx;

  /*
   * If the index is already full, then keep it full. We will convert
   * it to a sparse index on write, if possible.
   */
  if (istate->sparse_index == INDEX_EXPANDED)
    return;

  /*
   * If our index is sparse, but our new pattern set does not use
   * cone mode patterns, then we need to expand the index before we
   * continue. A NULL pattern set indicates a full expansion to a
   * full index.
   */
  if (pl && !pl->use_cone_patterns) {
    pl = NULL;
  } else {
    /*
     * We might contract file entries into sparse-directory
     * entries, and for that we will need the cache tree to
     * be recomputed.
     */
    cache_tree_free(&istate->cache_tree);

    /*
     * If there is a problem creating the cache tree, then we
     * need to expand to a full index since we cannot satisfy
     * the current request as a sparse index.
     */
    if (cache_tree_update(istate, 0))
      pl = NULL;
  }

  if (!pl && give_advice_on_expansion) {
    give_advice_on_expansion = 0;
    advise_if_enabled(ADVICE_SPARSE_INDEX_EXPANDED,
          _(ADVICE_MSG));
  }

  /*
   * A NULL pattern set indicates we are expanding a full index, so
   * we use a special region name that indicates the full expansion.
   * This is used by test cases, but also helps to differentiate the
   * two cases.
   */
  tr_region = pl ? "expand_index" : "ensure_full_index";
  trace2_region_enter("index", tr_region, istate->repo);

  /* initialize basics of new index */
  full = xcalloc(1, sizeof(struct index_state));
  memcpy(full, istate, sizeof(struct index_state));

  /*
   * This slightly-misnamed 'full' index might still be sparse if we
   * are only modifying the list of sparse directories. This hinges
   * on whether we have a non-NULL pattern list.
   */
  full->sparse_index = pl ? INDEX_PARTIALLY_SPARSE : INDEX_EXPANDED;

  /* then change the necessary things */
  full->cache_alloc = (3 * istate->cache_alloc) / 2;
  full->cache_nr = 0;
  ALLOC_ARRAY(full->cache, full->cache_alloc);

  ctx.write = full;
  ctx.pl = pl;

  for (i = 0; i < istate->cache_nr; i++) {
    struct cache_entry *ce = istate->cache[i];
    struct tree *tree;
    struct pathspec ps;
    int dtype;

    if (!S_ISSPARSEDIR(ce->ce_mode)) {
      set_index_entry(full, full->cache_nr++, ce);
      continue;
    }

    /* We now have a sparse directory entry. Should we expand? */
    if (pl &&
        path_matches_pattern_list(ce->name, ce->ce_namelen,
                NULL, &dtype,
                pl, istate) == NOT_MATCHED) {
      set_index_entry(full, full->cache_nr++, ce);
      continue;
    }

    if (!(ce->ce_flags & CE_SKIP_WORKTREE))
      warning(_("index entry is a directory, but not sparse (%08x)"),
        ce->ce_flags);

    /* recursively walk into cd->name */
    tree = lookup_tree(istate->repo, &ce->oid);

    memset(&ps, 0, sizeof(ps));
    ps.recursive = 1;
    ps.has_wildcard = 1;
    ps.max_depth = -1;

    strbuf_setlen(&base, 0);
    strbuf_add(&base, ce->name, strlen(ce->name));

    read_tree_at(istate->repo, tree, &base, 0, &ps,
           add_path_to_index, &ctx);

    /* free directory entries. full entries are re-used */
    discard_cache_entry(ce);
  }

  /* Copy back into original index. */
  memcpy(&istate->name_hash, &full->name_hash, sizeof(full->name_hash));
  memcpy(&istate->dir_hash, &full->dir_hash, sizeof(full->dir_hash));
  istate->sparse_index = pl ? INDEX_PARTIALLY_SPARSE : INDEX_EXPANDED;
  free(istate->cache);
  istate->cache = full->cache;
  istate->cache_nr = full->cache_nr;
  istate->cache_alloc = full->cache_alloc;
  istate->fsmonitor_has_run_once = 0;
  ewah_free(istate->fsmonitor_dirty);
  istate->fsmonitor_dirty = NULL;
  FREE_AND_NULL(istate->fsmonitor_last_update);

  strbuf_release(&base);
  free(full);

  /* Clear and recompute the cache-tree */
  cache_tree_free(&istate->cache_tree);
  cache_tree_update(istate, 0);

  trace2_region_leave("index", tr_region, istate->repo);
}

void ensure_full_index(struct index_state *istate)
{
  if (!istate)
    BUG("ensure_full_index() must get an index!");
  expand_index(istate, NULL);
}

void ensure_correct_sparsity(struct index_state *istate)
{
  /*
   * If the index can be sparse, make it sparse. Otherwise,
   * ensure the index is full.
   */
  if (is_sparse_index_allowed(istate, 0))
    convert_to_sparse(istate, 0);
  else
    ensure_full_index(istate);
}

struct path_found_data {
  /**
   * The path stored in 'dir', if non-empty, corresponds to the most-
   * recent path that we checked where:
   *
   *   1. The path should be a directory, according to the index.
   *   2. The path does not exist.
   *   3. The parent path _does_ exist. (This may be the root of the
   *      working directory.)
   */
  struct strbuf dir;
  size_t lstat_count;
};

#define PATH_FOUND_DATA_INIT { \
  .dir = STRBUF_INIT \
}

static void clear_path_found_data(struct path_found_data *data)
{
  strbuf_release(&data->dir);
}

/**
 * Return the length of the longest common substring that ends in a
 * slash ('/') to indicate the longest common parent directory. Returns
 * zero if no common directory exists.
 */
static size_t max_common_dir_prefix(const char *path1, const char *path2)
{
  size_t common_prefix = 0;
  for (size_t i = 0; path1[i] && path2[i]; i++) {
    if (path1[i] != path2[i])
      break;

    /*
     * If they agree at a directory separator, then add one
     * to make sure it is included in the common prefix string.
     */
    if (path1[i] == '/')
      common_prefix = i + 1;
  }

  return common_prefix;
}

static int path_found(const char *path, struct path_found_data *data)
{
  struct stat st;
  size_t common_prefix;

  /*
   * If data->dir is non-empty, then it contains a path that doesn't
   * exist, including an ending slash ('/'). If it is a prefix of 'path',
   * then we can return 0.
   */
  if (data->dir.len && !memcmp(path, data->dir.buf, data->dir.len))
    return 0;

  /*
   * Otherwise, we must check if the current path exists. If it does, then
   * return 1. The cached directory will be skipped until we come across
   * a missing path again.
   */
  data->lstat_count++;
  if (!lstat(path, &st))
    return 1;

  /*
   * At this point, we know that 'path' doesn't exist, and we know that
   * the parent directory of 'data->dir' does exist. Let's set 'data->dir'
   * to be the top-most non-existing directory of 'path'. If the first
   * parent of 'path' exists, then we will act as though 'path'
   * corresponds to a directory (by adding a slash).
   */
  common_prefix = max_common_dir_prefix(path, data->dir.buf);

  /*
   * At this point, 'path' and 'data->dir' have a common existing parent
   * directory given by path[0..common_prefix] (which could have length 0).
   * We "grow" the data->dir buffer by checking for existing directories
   * along 'path'.
   */

  strbuf_setlen(&data->dir, common_prefix);
  while (1) {
    /* Find the next directory in 'path'. */
    const char *rest = path + data->dir.len;
    const char *next_slash = strchr(rest, '/');

    /*
     * If there are no more slashes, then 'path' doesn't contain a
     * non-existent _parent_ directory. Set 'data->dir' to be equal
     * to 'path' plus an additional slash, so it can be used for
     * caching in the future. The filename of 'path' is considered
     * a non-existent directory.
     *
     * Note: if "{path}/" exists as a directory, then it will never
     * appear as a prefix of other callers to this method, assuming
     * the context from the clear_skip_worktree... methods. If this
     * method is reused, then this must be reconsidered.
     */
    if (!next_slash) {
      strbuf_addstr(&data->dir, rest);
      strbuf_addch(&data->dir, '/');
      break;
    }

    /*
     * Now that we have a slash, let's grow 'data->dir' to include
     * this slash, then test if we should stop.
     */
    strbuf_add(&data->dir, rest, next_slash - rest + 1);

    /* If the parent dir doesn't exist, then stop here. */
    data->lstat_count++;
    if (lstat(data->dir.buf, &st))
      return 0;
  }

  /*
   * At this point, 'data->dir' is equal to 'path' plus a slash character,
   * and the parent directory of 'path' definitely exists. Moreover, we
   * know that 'path' doesn't exist, or we would have returned 1 earlier.
   */
  return 0;
}

static int clear_skip_worktree_from_present_files_sparse(struct index_state *istate)
{
  struct path_found_data data = PATH_FOUND_DATA_INIT;

  int path_count = 0;
  int to_restart = 0;

  trace2_region_enter("index", "clear_skip_worktree_from_present_files_sparse",
          istate->repo);
  for (int i = 0; i < istate->cache_nr; i++) {
    struct cache_entry *ce = istate->cache[i];

    if (ce_skip_worktree(ce)) {
      path_count++;
      if (path_found(ce->name, &data)) {
        if (S_ISSPARSEDIR(ce->ce_mode)) {
          to_restart = 1;
          break;
        }
        ce->ce_flags &= ~CE_SKIP_WORKTREE;
      }
    }
  }

  trace2_data_intmax("index", istate->repo,
         "sparse_path_count", path_count);
  trace2_data_intmax("index", istate->repo,
         "sparse_lstat_count", data.lstat_count);
  trace2_region_leave("index", "clear_skip_worktree_from_present_files_sparse",
          istate->repo);
  clear_path_found_data(&data);
  return to_restart;
}

static void clear_skip_worktree_from_present_files_full(struct index_state *istate)
{
  struct path_found_data data = PATH_FOUND_DATA_INIT;

  int path_count = 0;

  trace2_region_enter("index", "clear_skip_worktree_from_present_files_full",
          istate->repo);
  for (int i = 0; i < istate->cache_nr; i++) {
    struct cache_entry *ce = istate->cache[i];

    if (S_ISSPARSEDIR(ce->ce_mode))
      BUG("ensure-full-index did not fully flatten?");

    if (ce_skip_worktree(ce)) {
      path_count++;
      if (path_found(ce->name, &data))
        ce->ce_flags &= ~CE_SKIP_WORKTREE;
    }
  }

  trace2_data_intmax("index", istate->repo,
         "full_path_count", path_count);
  trace2_data_intmax("index", istate->repo,
         "full_lstat_count", data.lstat_count);
  trace2_region_leave("index", "clear_skip_worktree_from_present_files_full",
          istate->repo);
  clear_path_found_data(&data);
}

void clear_skip_worktree_from_present_files(struct index_state *istate)
{
  struct repo_config_values *cfg = repo_config_values(the_repository);

  if (!cfg->apply_sparse_checkout ||
      cfg->sparse_expect_files_outside_of_patterns)
    return;

  if (clear_skip_worktree_from_present_files_sparse(istate)) {
    ensure_full_index(istate);
    clear_skip_worktree_from_present_files_full(istate);
  }
}

/*
 * This static global helps avoid infinite recursion between
 * expand_to_path() and index_file_exists().
 */
static int in_expand_to_path = 0;

void expand_to_path(struct index_state *istate,
        const char *path, size_t pathlen, int icase)
{
  struct strbuf path_mutable = STRBUF_INIT;
  size_t substr_len;

  /* prevent extra recursion */
  if (in_expand_to_path)
    return;

  if (!istate->sparse_index)
    return;

  in_expand_to_path = 1;

  /*
   * We only need to actually expand a region if the
   * following are both true:
   *
   * 1. 'path' is not already in the index.
   * 2. Some parent directory of 'path' is a sparse directory.
   */

  if (index_file_exists(istate, path, pathlen, icase))
    goto cleanup;

  strbuf_add(&path_mutable, path, pathlen);
  strbuf_addch(&path_mutable, '/');

  /* Check the name hash for all parent directories */
  substr_len = 0;
  while (substr_len < pathlen) {
    char temp;
    char *replace = strchr(path_mutable.buf + substr_len, '/');

    if (!replace)
      break;

    /* replace the character _after_ the slash */
    replace++;
    temp = *replace;
    *replace = '\0';
    substr_len = replace - path_mutable.buf;
    if (index_file_exists(istate, path_mutable.buf,
              substr_len, icase)) {
      /*
       * We found a parent directory in the name-hash
       * hashtable, because only sparse directory entries
       * have a trailing '/' character.  Since "path" wasn't
       * in the index, perhaps it exists within this
       * sparse-directory.  Expand accordingly.
       */
      ensure_full_index(istate);
      break;
    }

    *replace = temp;
  }

cleanup:
  strbuf_release(&path_mutable);
  in_expand_to_path = 0;
}

Coverage Report

Created: 2026-10-17 07:15