+void set_alternate_index_output(const char *name)
+{
+ alternate_index_output = name;
+}
+
+static int commit_locked_index(struct lock_file *lk)
+{
+ if (alternate_index_output)
+ return commit_lock_file_to(lk, alternate_index_output);
+ else
+ return commit_lock_file(lk);
+}
+
+static int do_write_locked_index(struct index_state *istate, struct lock_file *lock,
+ unsigned flags)
+{
+ int ret = do_write_index(istate, &lock->tempfile, 0);
+ if (ret)
+ return ret;
+ assert((flags & (COMMIT_LOCK | CLOSE_LOCK)) !=
+ (COMMIT_LOCK | CLOSE_LOCK));
+ if (flags & COMMIT_LOCK)
+ return commit_locked_index(lock);
+ else if (flags & CLOSE_LOCK)
+ return close_lock_file(lock);
+ else
+ return ret;
+}
+
+static int write_split_index(struct index_state *istate,
+ struct lock_file *lock,
+ unsigned flags)
+{
+ int ret;
+ prepare_to_write_split_index(istate);
+ ret = do_write_locked_index(istate, lock, flags);
+ finish_writing_split_index(istate);
+ return ret;
+}
+
+static const char *shared_index_expire = "2.weeks.ago";
+
+static unsigned long get_shared_index_expire_date(void)
+{
+ static unsigned long shared_index_expire_date;
+ static int shared_index_expire_date_prepared;
+
+ if (!shared_index_expire_date_prepared) {
+ git_config_get_expiry("splitindex.sharedindexexpire",
+ &shared_index_expire);
+ shared_index_expire_date = approxidate(shared_index_expire);
+ shared_index_expire_date_prepared = 1;
+ }
+
+ return shared_index_expire_date;
+}
+
+static int should_delete_shared_index(const char *shared_index_path)
+{
+ struct stat st;
+ unsigned long expiration;
+
+ /* Check timestamp */
+ expiration = get_shared_index_expire_date();
+ if (!expiration)
+ return 0;
+ if (stat(shared_index_path, &st))
+ return error_errno(_("could not stat '%s'"), shared_index_path);
+ if (st.st_mtime > expiration)
+ return 0;
+
+ return 1;
+}
+
+static int clean_shared_index_files(const char *current_hex)
+{
+ struct dirent *de;
+ DIR *dir = opendir(get_git_dir());
+
+ if (!dir)
+ return error_errno(_("unable to open git dir: %s"), get_git_dir());
+
+ while ((de = readdir(dir)) != NULL) {
+ const char *sha1_hex;
+ const char *shared_index_path;
+ if (!skip_prefix(de->d_name, "sharedindex.", &sha1_hex))
+ continue;
+ if (!strcmp(sha1_hex, current_hex))
+ continue;
+ shared_index_path = git_path("%s", de->d_name);
+ if (should_delete_shared_index(shared_index_path) > 0 &&
+ unlink(shared_index_path))
+ warning_errno(_("unable to unlink: %s"), shared_index_path);
+ }
+ closedir(dir);
+
+ return 0;
+}
+
+static struct tempfile temporary_sharedindex;
+
+static int write_shared_index(struct index_state *istate,
+ struct lock_file *lock, unsigned flags)
+{
+ struct split_index *si = istate->split_index;
+ int fd, ret;
+
+ fd = mks_tempfile(&temporary_sharedindex, git_path("sharedindex_XXXXXX"));
+ if (fd < 0) {
+ hashclr(si->base_sha1);
+ return do_write_locked_index(istate, lock, flags);
+ }
+ move_cache_to_base_index(istate);
+ ret = do_write_index(si->base, &temporary_sharedindex, 1);
+ if (ret) {
+ delete_tempfile(&temporary_sharedindex);
+ return ret;
+ }
+ ret = adjust_shared_perm(get_tempfile_path(&temporary_sharedindex));
+ if (ret) {
+ int save_errno = errno;
+ error("cannot fix permission bits on %s", get_tempfile_path(&temporary_sharedindex));
+ delete_tempfile(&temporary_sharedindex);
+ errno = save_errno;
+ return ret;
+ }
+ ret = rename_tempfile(&temporary_sharedindex,
+ git_path("sharedindex.%s", sha1_to_hex(si->base->sha1)));
+ if (!ret) {
+ hashcpy(si->base_sha1, si->base->sha1);
+ clean_shared_index_files(sha1_to_hex(si->base->sha1));
+ }
+
+ return ret;
+}
+
+static const int default_max_percent_split_change = 20;
+
+static int too_many_not_shared_entries(struct index_state *istate)
+{
+ int i, not_shared = 0;
+ int max_split = git_config_get_max_percent_split_change();
+
+ switch (max_split) {
+ case -1:
+ /* not or badly configured: use the default value */
+ max_split = default_max_percent_split_change;
+ break;
+ case 0:
+ return 1; /* 0% means always write a new shared index */
+ case 100:
+ return 0; /* 100% means never write a new shared index */
+ default:
+ break; /* just use the configured value */
+ }
+
+ /* Count not shared entries */
+ for (i = 0; i < istate->cache_nr; i++) {
+ struct cache_entry *ce = istate->cache[i];
+ if (!ce->index)
+ not_shared++;
+ }
+
+ return (int64_t)istate->cache_nr * max_split < (int64_t)not_shared * 100;
+}
+
+int write_locked_index(struct index_state *istate, struct lock_file *lock,
+ unsigned flags)
+{
+ int new_shared_index, ret;
+ struct split_index *si = istate->split_index;
+
+ if (!si || alternate_index_output ||
+ (istate->cache_changed & ~EXTMASK)) {
+ if (si)
+ hashclr(si->base_sha1);
+ return do_write_locked_index(istate, lock, flags);
+ }
+
+ if (getenv("GIT_TEST_SPLIT_INDEX")) {
+ int v = si->base_sha1[0];
+ if ((v & 15) < 6)
+ istate->cache_changed |= SPLIT_INDEX_ORDERED;
+ }
+ if (too_many_not_shared_entries(istate))
+ istate->cache_changed |= SPLIT_INDEX_ORDERED;
+
+ new_shared_index = istate->cache_changed & SPLIT_INDEX_ORDERED;
+
+ if (new_shared_index) {
+ ret = write_shared_index(istate, lock, flags);
+ if (ret)
+ return ret;
+ }
+
+ ret = write_split_index(istate, lock, flags);
+
+ /* Freshen the shared index only if the split-index was written */
+ if (!ret && !new_shared_index)
+ freshen_shared_index(sha1_to_hex(si->base_sha1), 1);
+
+ return ret;
+}
+