static inline unsigned char do_cache2(struct cache2 *self)
{
    uint32_t current_serial;
    int change_detected;
    unsigned char c;

    if (pthread_mutex_trylock(&self->lock)) {
        /* We are willing to accept some race in this context */
        return self->evaluate(self);
    }

    change_detected = check_cache(&self->cache_persist)
                   || check_cache(&self->cache_ro);
    current_serial = __system_property_area_serial();
    if (current_serial != self->serial) {
        change_detected = 1;
    }
    if (change_detected) {
        refresh_cache(&self->cache_persist, self->key_persist);
        refresh_cache(&self->cache_ro, self->key_ro);
        self->serial = current_serial;
    }
    c = self->evaluate(self);

    pthread_mutex_unlock(&self->lock);

    return c;
}

char android_log_timestamp()
{
    static struct cache r_time_cache = { NULL, -1, 0 };
    static struct cache p_time_cache = { NULL, -1, 0 };
    char retval;

    if (pthread_mutex_trylock(&lock_timestamp)) {
        /* We are willing to accept some race in this context */
        if (!(retval = p_time_cache.c)) {
            retval = r_time_cache.c;
        }
    } else {
        static uint32_t serial;
        uint32_t current_serial = __system_property_area_serial();
        if (current_serial != serial) {
            refresh_cache(&r_time_cache, "ro.logd.timestamp");
            refresh_cache(&p_time_cache, "persist.logd.timestamp");
            serial = current_serial;
        }
        if (!(retval = p_time_cache.c)) {
            retval = r_time_cache.c;
        }

        pthread_mutex_unlock(&lock_timestamp);
    }

    return tolower(retval ?: 'r');
}

static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
{
	unsigned char result_tree[20], result_commit[20];
	struct commit_list *parents, **pptr = &parents;
	static struct lock_file lock;

	hold_locked_index(&lock, 1);
	refresh_cache(REFRESH_QUIET);
	if (active_cache_changed &&
	    write_locked_index(&the_index, &lock, COMMIT_LOCK))
		return error(_("Unable to write index."));
	rollback_lock_file(&lock);

	write_tree_trivial(result_tree);
	printf(_("Wonderful.\n"));
	pptr = commit_list_append(head, pptr);
	pptr = commit_list_append(remoteheads->item, pptr);
	prepare_to_commit(remoteheads);
	if (commit_tree(merge_msg.buf, merge_msg.len, result_tree, parents,
			result_commit, NULL, sign_commit))
		die(_("failed to write commit object"));
	finish(head, remoteheads, result_commit, "In-index merge");
	drop_save();
	return 0;
}

/**
 * If the work tree has unstaged or uncommitted changes, dies with the
 * appropriate message.
 */
static void die_on_unclean_work_tree(const char *prefix)
{
	struct lock_file *lock_file = xcalloc(1, sizeof(*lock_file));
	int do_die = 0;

	hold_locked_index(lock_file, 0);
	refresh_cache(REFRESH_QUIET);
	update_index_if_able(&the_index, lock_file);
	rollback_lock_file(lock_file);

	if (has_unstaged_changes(prefix)) {
		error(_("Cannot pull with rebase: You have unstaged changes."));
		do_die = 1;
	}

	if (has_uncommitted_changes(prefix)) {
		if (do_die)
			error(_("Additionally, your index contains uncommitted changes."));
		else
			error(_("Cannot pull with rebase: Your index contains uncommitted changes."));
		do_die = 1;
	}

	if (do_die)
		exit(1);
}

static int refresh(struct refresh_params *o, unsigned int flag)
{
	setup_work_tree();
	read_cache_preload(NULL);
	*o->has_errors |= refresh_cache(o->flags | flag);
	return 0;
}

static int try_merge_strategy(const char *strategy, struct commit_list *common,
			      const char *head_arg)
{
	int index_fd;
	struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));

	index_fd = hold_locked_index(lock, 1);
	refresh_cache(REFRESH_QUIET);
	if (active_cache_changed &&
			(write_cache(index_fd, active_cache, active_nr) ||
			 commit_locked_index(lock)))
		return error(_("Unable to write index."));
	rollback_lock_file(lock);

	if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
		int clean, x;
		struct commit *result;
		struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
		int index_fd;
		struct commit_list *reversed = NULL;
		struct merge_options o;
		struct commit_list *j;

		if (remoteheads->next) {
			error(_("Not handling anything other than two heads merge."));
			return 2;
		}

		init_merge_options(&o);
		if (!strcmp(strategy, "subtree"))
			o.subtree_shift = "";

		o.renormalize = option_renormalize;
		o.show_rename_progress =
			show_progress == -1 ? isatty(2) : show_progress;

		for (x = 0; x < xopts_nr; x++)
			if (parse_merge_opt(&o, xopts[x]))
				die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);

		o.branch1 = head_arg;
		o.branch2 = remoteheads->item->util;

		for (j = common; j; j = j->next)
			commit_list_insert(j->item, &reversed);

		index_fd = hold_locked_index(lock, 1);
		clean = merge_recursive(&o, lookup_commit(head),
				remoteheads->item, reversed, &result);
		if (active_cache_changed &&
				(write_cache(index_fd, active_cache, active_nr) ||
				 commit_locked_index(lock)))
			die (_("unable to write %s"), get_index_file());
		rollback_lock_file(lock);
		return clean ? 0 : 1;
	} else {
		return try_merge_command(strategy, xopts_nr, xopts,
						common, head_arg, remoteheads);
	}
}

static void refresh_cache_or_die(int refresh_flags)
{
	/*
	 * refresh_flags contains REFRESH_QUIET, so the only errors
	 * are for unmerged entries.
	 */
	if (refresh_cache(refresh_flags | REFRESH_IN_PORCELAIN))
		die_resolve_conflict("commit");
}

static void refresh_index_quietly(void)
{
	struct lock_file lock_file = LOCK_INIT;
	int fd;

	fd = hold_locked_index(&lock_file, 0);
	if (fd < 0)
		return;
	discard_cache();
	read_cache();
	refresh_cache(REFRESH_QUIET|REFRESH_UNMERGED);
	update_index_if_able(&the_index, &lock_file);
}

int checkout_fast_forward(const unsigned char *head,
			  const unsigned char *remote,
			  int overwrite_ignore)
{
	struct tree *trees[MAX_UNPACK_TREES];
	struct unpack_trees_options opts;
	struct tree_desc t[MAX_UNPACK_TREES];
	int i, nr_trees = 0;
	struct dir_struct dir;
	struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));

	refresh_cache(REFRESH_QUIET);

	hold_locked_index(lock_file, 1);

	memset(&trees, 0, sizeof(trees));
	memset(&opts, 0, sizeof(opts));
	memset(&t, 0, sizeof(t));
	if (overwrite_ignore) {
		memset(&dir, 0, sizeof(dir));
		dir.flags |= DIR_SHOW_IGNORED;
		setup_standard_excludes(&dir);
		opts.dir = &dir;
	}

	opts.head_idx = 1;
	opts.src_index = &the_index;
	opts.dst_index = &the_index;
	opts.update = 1;
	opts.verbose_update = 1;
	opts.merge = 1;
	opts.fn = twoway_merge;
	setup_unpack_trees_porcelain(&opts, "merge");

	trees[nr_trees] = parse_tree_indirect(head);
	if (!trees[nr_trees++])
		return -1;
	trees[nr_trees] = parse_tree_indirect(remote);
	if (!trees[nr_trees++])
		return -1;
	for (i = 0; i < nr_trees; i++) {
		parse_tree(trees[i]);
		init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
	}
	if (unpack_trees(nr_trees, t, &opts))
		return -1;
	if (write_locked_index(&the_index, lock_file, COMMIT_LOCK))
		die(_("unable to write new index file"));
	return 0;
}

static void refresh_index_quietly(void)
{
	struct lock_file *lock_file;
	int fd;

	lock_file = xcalloc(1, sizeof(struct lock_file));
	fd = hold_locked_index(lock_file, 0);
	if (fd < 0)
		return;
	discard_cache();
	read_cache();
	refresh_cache(REFRESH_QUIET|REFRESH_UNMERGED);
	update_index_if_able(&the_index, lock_file);
}

static int checkout_fast_forward(unsigned char *head, unsigned char *remote)
{
	struct tree *trees[MAX_UNPACK_TREES];
	struct unpack_trees_options opts;
	struct tree_desc t[MAX_UNPACK_TREES];
	int i, fd, nr_trees = 0;
	struct dir_struct dir;
	struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));

	refresh_cache(REFRESH_QUIET);

	fd = hold_locked_index(lock_file, 1);

	memset(&trees, 0, sizeof(trees));
	memset(&opts, 0, sizeof(opts));
	memset(&t, 0, sizeof(t));
	memset(&dir, 0, sizeof(dir));
	dir.flags |= DIR_SHOW_IGNORED;
	dir.exclude_per_dir = ".gitignore";
	opts.dir = &dir;

	opts.head_idx = 1;
	opts.src_index = &the_index;
	opts.dst_index = &the_index;
	opts.update = 1;
	opts.verbose_update = 1;
	opts.merge = 1;
	opts.fn = twoway_merge;
	opts.msgs = get_porcelain_error_msgs();

	trees[nr_trees] = parse_tree_indirect(head);
	if (!trees[nr_trees++])
		return -1;
	trees[nr_trees] = parse_tree_indirect(remote);
	if (!trees[nr_trees++])
		return -1;
	for (i = 0; i < nr_trees; i++) {
		parse_tree(trees[i]);
		init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
	}
	if (unpack_trees(nr_trees, t, &opts))
		return -1;
	if (write_cache(fd, active_cache, active_nr) ||
		commit_locked_index(lock_file))
		die("unable to write new index file");
	return 0;
}

static int update_index_refresh(int fd, struct lock_file *index_lock, int flags)
{
	int result;

	if (!index_lock) {
		index_lock = xcalloc(1, sizeof(struct lock_file));
		fd = hold_locked_index(index_lock, 1);
	}

	if (read_cache() < 0)
		return error("Could not read index");

	result = refresh_cache(flags) ? 1 : 0;
	if (write_cache(fd, active_cache, active_nr) ||
			commit_locked_index(index_lock))
		return error ("Could not refresh index");
	return result;
}

static void refresh_index_quietly(void)
{
	struct lock_file *lock_file;
	int fd;

	lock_file = xcalloc(1, sizeof(struct lock_file));
	fd = hold_locked_index(lock_file, 0);
	if (fd < 0)
		return;
	discard_cache();
	read_cache();
	refresh_cache(REFRESH_QUIET|REFRESH_UNMERGED);

	if (active_cache_changed &&
	    !write_cache(fd, active_cache, active_nr))
		commit_locked_index(lock_file);

	rollback_lock_file(lock_file);
}

static void restore_state(void)
{
	struct strbuf sb = STRBUF_INIT;
	const char *args[] = { "stash", "apply", NULL, NULL };

	if (is_null_sha1(stash))
		return;

	reset_hard(head, 1);

	args[2] = sha1_to_hex(stash);

	/*
	 * It is OK to ignore error here, for example when there was
	 * nothing to restore.
	 */
	run_command_v_opt(args, RUN_GIT_CMD);

	strbuf_release(&sb);
	refresh_cache(REFRESH_QUIET);
}

static int reset_tree(struct object_id *i_tree, int update, int reset)
{
	int nr_trees = 1;
	struct unpack_trees_options opts;
	struct tree_desc t[MAX_UNPACK_TREES];
	struct tree *tree;
	struct lock_file lock_file = LOCK_INIT;

	read_cache_preload(NULL);
	if (refresh_cache(REFRESH_QUIET))
		return -1;

	hold_locked_index(&lock_file, LOCK_DIE_ON_ERROR);

	memset(&opts, 0, sizeof(opts));

	tree = parse_tree_indirect(i_tree);
	if (parse_tree(tree))
		return -1;

	init_tree_desc(t, tree->buffer, tree->size);

	opts.head_idx = 1;
	opts.src_index = &the_index;
	opts.dst_index = &the_index;
	opts.merge = 1;
	opts.reset = reset;
	opts.update = update;
	opts.fn = oneway_merge;

	if (unpack_trees(nr_trees, t, &opts))
		return -1;

	if (write_locked_index(&the_index, &lock_file, COMMIT_LOCK))
		return error(_("unable to write new index file"));

	return 0;
}

static int merge_working_tree(const struct checkout_opts *opts,
			      struct branch_info *old_branch_info,
			      struct branch_info *new_branch_info,
			      int *writeout_error)
{
	int ret;
	struct lock_file lock_file = LOCK_INIT;

	hold_locked_index(&lock_file, LOCK_DIE_ON_ERROR);
	if (read_cache_preload(NULL) < 0)
		return error(_("index file corrupt"));

	resolve_undo_clear();
	if (opts->force) {
		ret = reset_tree(get_commit_tree(new_branch_info->commit),
				 opts, 1, writeout_error);
		if (ret)
			return ret;
	} else {
		struct tree_desc trees[2];
		struct tree *tree;
		struct unpack_trees_options topts;

		memset(&topts, 0, sizeof(topts));
		topts.head_idx = -1;
		topts.src_index = &the_index;
		topts.dst_index = &the_index;

		setup_unpack_trees_porcelain(&topts, "checkout");

		refresh_cache(REFRESH_QUIET);

		if (unmerged_cache()) {
			error(_("you need to resolve your current index first"));
			return 1;
		}

		/* 2-way merge to the new branch */
		topts.initial_checkout = is_cache_unborn();
		topts.update = 1;
		topts.merge = 1;
		topts.gently = opts->merge && old_branch_info->commit;
		topts.verbose_update = opts->show_progress;
		topts.fn = twoway_merge;
		if (opts->overwrite_ignore) {
			topts.dir = xcalloc(1, sizeof(*topts.dir));
			topts.dir->flags |= DIR_SHOW_IGNORED;
			setup_standard_excludes(topts.dir);
		}
		tree = parse_tree_indirect(old_branch_info->commit ?
					   &old_branch_info->commit->object.oid :
					   the_hash_algo->empty_tree);
		init_tree_desc(&trees[0], tree->buffer, tree->size);
		tree = parse_tree_indirect(&new_branch_info->commit->object.oid);
		init_tree_desc(&trees[1], tree->buffer, tree->size);

		ret = unpack_trees(2, trees, &topts);
		clear_unpack_trees_porcelain(&topts);
		if (ret == -1) {
			/*
			 * Unpack couldn't do a trivial merge; either
			 * give up or do a real merge, depending on
			 * whether the merge flag was used.
			 */
			struct tree *result;
			struct tree *work;
			struct merge_options o;
			if (!opts->merge)
				return 1;

			/*
			 * Without old_branch_info->commit, the below is the same as
			 * the two-tree unpack we already tried and failed.
			 */
			if (!old_branch_info->commit)
				return 1;

			/* Do more real merge */

			/*
			 * We update the index fully, then write the
			 * tree from the index, then merge the new
			 * branch with the current tree, with the old
			 * branch as the base. Then we reset the index
			 * (but not the working tree) to the new
			 * branch, leaving the working tree as the
			 * merged version, but skipping unmerged
			 * entries in the index.
			 */

			add_files_to_cache(NULL, NULL, 0);
			/*
			 * NEEDSWORK: carrying over local changes
			 * when branches have different end-of-line
			 * normalization (or clean+smudge rules) is
			 * a pain; plumb in an option to set
			 * o.renormalize?
			 */
			init_merge_options(&o, the_repository);
			o.verbosity = 0;
//.........这里部分代码省略.........

static int __android_log_level(const char *tag, int default_prio)
{
    /* sizeof() is used on this array below */
    static const char log_namespace[] = "persist.log.tag.";
    static const size_t base_offset = 8; /* skip "persist." */
    /* calculate the size of our key temporary buffer */
    const size_t taglen = (tag && *tag) ? strlen(tag) : 0;
    /* sizeof(log_namespace) = strlen(log_namespace) + 1 */
    char key[sizeof(log_namespace) + taglen]; /* may be > PROPERTY_KEY_MAX */
    char *kp;
    size_t i;
    char c = 0;
    /*
     * Single layer cache of four properties. Priorities are:
     *    log.tag.<tag>
     *    persist.log.tag.<tag>
     *    log.tag
     *    persist.log.tag
     * Where the missing tag matches all tags and becomes the
     * system global default. We do not support ro.log.tag* .
     */
    static char last_tag[PROP_NAME_MAX];
    static uint32_t global_serial;
    /* some compilers erroneously see uninitialized use. !not_locked */
    uint32_t current_global_serial = 0;
    static struct cache tag_cache[2];
    static struct cache global_cache[2];
    int change_detected;
    int global_change_detected;
    int not_locked;

    strcpy(key, log_namespace);

    global_change_detected = change_detected = not_locked = lock();

    if (!not_locked) {
        /*
         *  check all known serial numbers to changes.
         */
        for (i = 0; i < (sizeof(tag_cache) / sizeof(tag_cache[0])); ++i) {
            if (check_cache(&tag_cache[i])) {
                change_detected = 1;
            }
        }
        for (i = 0; i < (sizeof(global_cache) / sizeof(global_cache[0])); ++i) {
            if (check_cache(&global_cache[i])) {
                global_change_detected = 1;
            }
        }

        current_global_serial = __system_property_area_serial();
        if (current_global_serial != global_serial) {
            change_detected = 1;
            global_change_detected = 1;
        }
    }

    if (taglen) {
        int local_change_detected = change_detected;
        if (!not_locked) {
            if (!last_tag[0]
                    || (last_tag[0] != tag[0])
                    || strncmp(last_tag + 1, tag + 1, sizeof(last_tag) - 1)) {
                /* invalidate log.tag.<tag> cache */
                for (i = 0; i < (sizeof(tag_cache) / sizeof(tag_cache[0])); ++i) {
                    tag_cache[i].pinfo = NULL;
                    tag_cache[i].c = '\0';
                }
                last_tag[0] = '\0';
                local_change_detected = 1;
            }
            if (!last_tag[0]) {
                strncpy(last_tag, tag, sizeof(last_tag));
            }
        }
        strcpy(key + sizeof(log_namespace) - 1, tag);

        kp = key;
        for (i = 0; i < (sizeof(tag_cache) / sizeof(tag_cache[0])); ++i) {
            struct cache *cache = &tag_cache[i];
            struct cache temp_cache;

            if (not_locked) {
                temp_cache.pinfo = NULL;
                temp_cache.c = '\0';
                cache = &temp_cache;
            }
            if (local_change_detected) {
                refresh_cache(cache, kp);
            }

            if (cache->c) {
                c = cache->c;
                break;
            }

            kp = key + base_offset;
        }
    }

//.........这里部分代码省略.........

//.........这里部分代码省略.........
				find_unique_abbrev(remoteheads->item->object.sha1,
				DEFAULT_ABBREV));
		strbuf_addstr(&msg, "Fast-forward");
		if (have_message)
			strbuf_addstr(&msg,
				" (no commit created; -m option ignored)");
		commit = remoteheads->item;
		if (!commit) {
			ret = 1;
			goto done;
		}

		if (checkout_fast_forward(head_commit->object.sha1,
					  commit->object.sha1,
					  overwrite_ignore)) {
			ret = 1;
			goto done;
		}

		finish(head_commit, remoteheads, commit->object.sha1, msg.buf);
		drop_save();
		goto done;
	} else if (!remoteheads->next && common->next)
		;
		/*
		 * We are not doing octopus and not fast-forward.  Need
		 * a real merge.
		 */
	else if (!remoteheads->next && !common->next && option_commit) {
		/*
		 * We are not doing octopus, not fast-forward, and have
		 * only one common.
		 */
		refresh_cache(REFRESH_QUIET);
		if (allow_trivial && !fast_forward_only) {
			/* See if it is really trivial. */
			git_committer_info(IDENT_STRICT);
			printf(_("Trying really trivial in-index merge...\n"));
			if (!read_tree_trivial(common->item->object.sha1,
					       head_commit->object.sha1,
					       remoteheads->item->object.sha1)) {
				ret = merge_trivial(head_commit, remoteheads);
				goto done;
			}
			printf(_("Nope.\n"));
		}
	} else {
		/*
		 * An octopus.  If we can reach all the remote we are up
		 * to date.
		 */
		int up_to_date = 1;
		struct commit_list *j;

		for (j = remoteheads; j; j = j->next) {
			struct commit_list *common_one;

			/*
			 * Here we *have* to calculate the individual
			 * merge_bases again, otherwise "git merge HEAD^
			 * HEAD^^" would be missed.
			 */
			common_one = get_merge_bases(head_commit, j->item, 1);
			if (hashcmp(common_one->item->object.sha1,
				j->item->object.sha1)) {
				up_to_date = 0;

int cmd_update_index(int argc, const char **argv, const char *prefix)
{
	int i, newfd, entries, has_errors = 0, line_termination = '\n';
	int allow_options = 1;
	int read_from_stdin = 0;
	int prefix_length = prefix ? strlen(prefix) : 0;
	char set_executable_bit = 0;
	unsigned int refresh_flags = 0;
	int lock_error = 0;
	struct lock_file *lock_file;

	git_config(git_default_config, NULL);

	/* We can't free this memory, it becomes part of a linked list parsed atexit() */
	lock_file = xcalloc(1, sizeof(struct lock_file));

	newfd = hold_locked_index(lock_file, 0);
	if (newfd < 0)
		lock_error = errno;

	entries = read_cache();
	if (entries < 0)
		die("cache corrupted");

	for (i = 1 ; i < argc; i++) {
		const char *path = argv[i];
		const char *p;

		if (allow_options && *path == '-') {
			if (!strcmp(path, "--")) {
				allow_options = 0;
				continue;
			}
			if (!strcmp(path, "-q")) {
				refresh_flags |= REFRESH_QUIET;
				continue;
			}
			if (!strcmp(path, "--ignore-submodules")) {
				refresh_flags |= REFRESH_IGNORE_SUBMODULES;
				continue;
			}
			if (!strcmp(path, "--add")) {
				allow_add = 1;
				continue;
			}
			if (!strcmp(path, "--replace")) {
				allow_replace = 1;
				continue;
			}
			if (!strcmp(path, "--remove")) {
				allow_remove = 1;
				continue;
			}
			if (!strcmp(path, "--unmerged")) {
				refresh_flags |= REFRESH_UNMERGED;
				continue;
			}
			if (!strcmp(path, "--refresh")) {
				setup_work_tree();
				has_errors |= refresh_cache(refresh_flags);
				continue;
			}
			if (!strcmp(path, "--really-refresh")) {
				setup_work_tree();
				has_errors |= refresh_cache(REFRESH_REALLY | refresh_flags);
				continue;
			}
			if (!strcmp(path, "--cacheinfo")) {
				unsigned char sha1[20];
				unsigned int mode;

				if (i+3 >= argc)
					die("git update-index: --cacheinfo <mode> <sha1> <path>");

				if (strtoul_ui(argv[i+1], 8, &mode) ||
				    get_sha1_hex(argv[i+2], sha1) ||
				    add_cacheinfo(mode, sha1, argv[i+3], 0))
					die("git update-index: --cacheinfo"
					    " cannot add %s", argv[i+3]);
				i += 3;
				continue;
			}
			if (!strcmp(path, "--chmod=-x") ||
			    !strcmp(path, "--chmod=+x")) {
				if (argc <= i+1)
					die("git update-index: %s <path>", path);
				set_executable_bit = path[8];
				continue;
			}
			if (!strcmp(path, "--assume-unchanged")) {
				mark_valid_only = MARK_VALID;
				continue;
			}
			if (!strcmp(path, "--no-assume-unchanged")) {
				mark_valid_only = UNMARK_VALID;
				continue;
			}
			if (!strcmp(path, "--info-only")) {
				info_only = 1;
				continue;
//.........这里部分代码省略.........

static char *prepare_index(int argc, const char **argv, const char *prefix)
{
	int fd;
	struct path_list partial;
	const char **pathspec = NULL;

	if (interactive) {
		interactive_add(argc, argv, prefix);
		commit_style = COMMIT_AS_IS;
		return get_index_file();
	}

	if (read_cache() < 0)
		die("index file corrupt");

	if (*argv)
		pathspec = get_pathspec(prefix, argv);

	/*
	 * Non partial, non as-is commit.
	 *
	 * (1) get the real index;
	 * (2) update the_index as necessary;
	 * (3) write the_index out to the real index (still locked);
	 * (4) return the name of the locked index file.
	 *
	 * The caller should run hooks on the locked real index, and
	 * (A) if all goes well, commit the real index;
	 * (B) on failure, rollback the real index.
	 */
	if (all || (also && pathspec && *pathspec)) {
		int fd = hold_locked_index(&index_lock, 1);
		add_files_to_cache(0, also ? prefix : NULL, pathspec);
		refresh_cache(REFRESH_QUIET);
		if (write_cache(fd, active_cache, active_nr) ||
		    close_lock_file(&index_lock))
			die("unable to write new_index file");
		commit_style = COMMIT_NORMAL;
		return index_lock.filename;
	}

	/*
	 * As-is commit.
	 *
	 * (1) return the name of the real index file.
	 *
	 * The caller should run hooks on the real index, and run
	 * hooks on the real index, and create commit from the_index.
	 * We still need to refresh the index here.
	 */
	if (!pathspec || !*pathspec) {
		fd = hold_locked_index(&index_lock, 1);
		refresh_cache(REFRESH_QUIET);
		if (write_cache(fd, active_cache, active_nr) ||
		    commit_locked_index(&index_lock))
			die("unable to write new_index file");
		commit_style = COMMIT_AS_IS;
		return get_index_file();
	}

	/*
	 * A partial commit.
	 *
	 * (0) find the set of affected paths;
	 * (1) get lock on the real index file;
	 * (2) update the_index with the given paths;
	 * (3) write the_index out to the real index (still locked);
	 * (4) get lock on the false index file;
	 * (5) reset the_index from HEAD;
	 * (6) update the_index the same way as (2);
	 * (7) write the_index out to the false index file;
	 * (8) return the name of the false index file (still locked);
	 *
	 * The caller should run hooks on the locked false index, and
	 * create commit from it.  Then
	 * (A) if all goes well, commit the real index;
	 * (B) on failure, rollback the real index;
	 * In either case, rollback the false index.
	 */
	commit_style = COMMIT_PARTIAL;

	if (file_exists(git_path("MERGE_HEAD")))
		die("cannot do a partial commit during a merge.");

	memset(&partial, 0, sizeof(partial));
	partial.strdup_paths = 1;
	if (list_paths(&partial, initial_commit ? NULL : "HEAD", prefix, pathspec))
		exit(1);

	discard_cache();
	if (read_cache() < 0)
		die("cannot read the index");

	fd = hold_locked_index(&index_lock, 1);
	add_remove_files(&partial);
	refresh_cache(REFRESH_QUIET);
	if (write_cache(fd, active_cache, active_nr) ||
	    close_lock_file(&index_lock))
		die("unable to write new_index file");

//.........这里部分代码省略.........