index-helper: optionally automatically run

Introduce a new config option, indexhelper.autorun, to automatically
run git index-helper before starting up a builtin git command.  This
enables users to keep index-helper running without manual
intervention.

Signed-off-by: David Turner <dturner@twopensource.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

3 files changed, 57 insertions, 2 deletions

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 15001ce14b..385ea664fc 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -1856,6 +1856,10 @@ index.version::
 	Specify the version with which new index files should be
 	initialized.  This does not affect existing repositories.
 
+indexhelper.autorun::
+	Automatically run git index-helper when any builtin git
+	command is run inside a repository.
+
 init.templateDir::
 	Specify the directory from which templates will be copied.
 	(See the "TEMPLATE DIRECTORY" section of linkgit:git-init[1].)
diff --git a/read-cache.c b/read-cache.c
index 8141559300..fde778b074 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -22,6 +22,7 @@
 #include "pkt-line.h"
 #include "sigchain.h"
 #include "ewah/ewok.h"
+#include "run-command.h"
 
 static struct cache_entry *refresh_cache_entry(struct cache_entry *ce,
 					       unsigned int options);
@@ -1733,6 +1734,31 @@ static void post_read_index_from(struct index_state *istate)
 	tweak_untracked_cache(istate);
 }
 
+static int want_auto_index_helper(void)
+{
+	int want = -1;
+	const char *value = NULL;
+	const char *key = "indexhelper.autorun";
+
+	if (git_config_key_is_valid(key) &&
+	    !git_config_get_value(key, &value)) {
+		int b = git_config_maybe_bool(key, value);
+		want = b >= 0 ? b : 0;
+	}
+	return want;
+}
+
+static void autorun_index_helper(void)
+{
+	const char *argv[] = {"git-index-helper", "--detach", "--autorun", NULL};
+	if (want_auto_index_helper() <= 0)
+		return;
+
+	if (run_command_v_opt(argv,
+			      RUN_SILENT_EXEC_FAILURE | RUN_CLEAN_ON_EXIT))
+		warning(_("You specified indexhelper.autorun, but running git-index-helper failed."));
+}
+
 /* in ms */
 #define WATCHMAN_TIMEOUT 1000
 
@@ -1804,6 +1830,7 @@ static int poke_daemon(struct index_state *istate,
 	if (fd < 0) {
 		warning("Failed to connect to index-helper socket");
 		unlink(git_path("index-helper.sock"));
+		autorun_index_helper();
 		return -1;
 	}
 	sigchain_push(SIGPIPE, SIG_IGN);
@@ -1843,9 +1870,13 @@ static int try_shm(struct index_state *istate)
 	int fd = -1;
 
 	if (!is_main_index(istate) ||
-	    old_size <= 20 ||
-	    stat(git_path("index-helper.sock"), &st))
+	    old_size <= 20)
 		return -1;
+
+	if (stat(git_path("index-helper.sock"), &st)) {
+		autorun_index_helper();
+		return -1;
+	}
 	if (poke_daemon(istate, &st, 0))
 		return -1;
 	sha1 = (unsigned char *)istate->mmap + old_size - 20;
diff --git a/t/t7900-index-helper.sh b/t/t7900-index-helper.sh
index 7f72e94c7e..15ba612d2e 100755
--- a/t/t7900-index-helper.sh
+++ b/t/t7900-index-helper.sh
@@ -18,6 +18,9 @@ test $? = 129 ||
 }
 
 test_expect_success 'index-helper smoke test' '
+	# We need an existing commit so that the index exists (otherwise,
+	# the index-helper will not be autostarted)
+	test_commit x &&
 	git index-helper --exit-after 1 &&
 	test_path_is_missing .git/index-helper.sock
 '
@@ -48,4 +51,21 @@ test_expect_success 'index-helper is quiet with --autorun' '
 	git index-helper --autorun
 '
 
+test_expect_success 'index-helper autorun works' '
+	test_when_finished "git index-helper --kill" &&
+	rm -f .git/index-helper.sock &&
+	git status &&
+	test_path_is_missing .git/index-helper.sock &&
+	test_config indexhelper.autorun true &&
+	git status &&
+	test -S .git/index-helper.sock &&
+	git status 2>err &&
+	test -S .git/index-helper.sock &&
+	test_must_be_empty err &&
+	git index-helper --kill &&
+	test_config indexhelper.autorun false &&
+	git status &&
+	test_path_is_missing .git/index-helper.sock
+'
+
 test_done