Merge branch 'status-no-lock-index'

This branch allows third-party tools to call `git status
--no-lock-index` to avoid lock contention with the interactive Git usage
of the actual human user.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Documentation/git-status.txt

@@ -111,6 +111,11 @@ configuration variable documented in linkgit:git-config[1].
 	without options are equivalent to 'always' and 'never'
 	respectively.
 
+--no-lock-index::
+--lock-index::
+	Specifies whether `git status` should try to lock the index and
+	update it afterwards if any changes were detected. Defaults to
+	`--lock-index`.
 
 OUTPUT
 ------

builtin/commit.c

@@ -1335,6 +1335,7 @@ static int git_status_config(const char *k, const char *v, void *cb)
 
 int cmd_status(int argc, const char **argv, const char *prefix)
 {
+	static int no_lock_index = 0;
 	static struct wt_status s;
 	int fd;
 	struct object_id oid;
@@ -1364,6 +1365,8 @@ int cmd_status(int argc, const char **argv, const char *prefix)
 		  N_("ignore changes to submodules, optional when: all, dirty, untracked. (Default: all)"),
 		  PARSE_OPT_OPTARG, NULL, (intptr_t)"all" },
 		OPT_COLUMN(0, "column", &s.colopts, N_("list untracked files in columns")),
+		OPT_BOOL(0, "no-lock-index", &no_lock_index,
+			 N_("do not lock the index")),
 		OPT_END(),
 	};
 
@@ -1388,7 +1391,7 @@ int cmd_status(int argc, const char **argv, const char *prefix)
 	read_cache_preload(&s.pathspec);
 	refresh_index(&the_index, REFRESH_QUIET|REFRESH_UNMERGED, &s.pathspec, NULL, NULL);
 
-	fd = hold_locked_index(&index_lock, 0);
+	fd = no_lock_index ? -1 : hold_locked_index(&index_lock, 0);
 
 	s.is_initial = get_oid(s.reference, &oid) ? 1 : 0;
 	if (!s.is_initial)

t/t7508-status.sh

@@ -1670,4 +1670,15 @@ test_expect_success '"Initial commit" should not be noted in commit template' '
 	test_i18ngrep ! "Initial commit" output
 '
 
+test_expect_success '--no-lock-index' '
+	test_commit some-file &&
+	test-chmtime =1234567890 .git/index &&
+	git status --no-lock-index &&
+	test-chmtime -v +0 .git/index >out &&
+	grep ^1234567890 out &&
+	git status &&
+	test-chmtime -v +0 .git/index >out &&
+	! grep ^1234567890 out
+'
+
 test_done