repack: add config to skip updating server info

By default, git-repack(1) will update server info that is required by
the dumb HTTP transport. This can be skipped by passing the `-n` flag,
but what we're noticably missing is a config option to permanently
disable updating this information.

Add a new option "repack.updateServerInfo" which can be used to disable
the logic. Most hosting providers have turned off the dumb HTTP protocol
anyway, and on the client-side it woudln't typically be useful either.
Giving a persistent way to disable this feature thus makes quite some
sense to avoid wasting compute cycles and storage.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config/repack.txt

@@ -25,3 +25,8 @@ repack.writeBitmaps::
 	space and extra time spent on the initial repack.  This has
 	no effect if multiple packfiles are created.
 	Defaults to true on bare repos, false otherwise.
+
+repack.updateServerInfo::
+	If set to false, linkgit:git-repack[1] will not run
+	linkgit:git-update-server-info[1]. Defaults to true. Can be overridden
+	when true by the `-n` option of linkgit:git-repack[1].

builtin/repack.c

@@ -22,6 +22,7 @@ static int delta_base_offset = 1;
 static int pack_kept_objects = -1;
 static int write_bitmaps = -1;
 static int use_delta_islands;
+static int run_update_server_info = 1;
 static char *packdir, *packtmp_name, *packtmp;
 
 static const char *const git_repack_usage[] = {
@@ -54,6 +55,10 @@ static int repack_config(const char *var, const char *value, void *cb)
 		use_delta_islands = git_config_bool(var, value);
 		return 0;
 	}
+	if (strcmp(var, "repack.updateserverinfo") == 0) {
+		run_update_server_info = git_config_bool(var, value);
+		return 0;
+	}
 	return git_default_config(var, value, cb);
 }
 
@@ -620,7 +625,6 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
 	const char *unpack_unreachable = NULL;
 	int keep_unreachable = 0;
 	struct string_list keep_pack_list = STRING_LIST_INIT_NODUP;
-	int run_update_server_info = 1;
 	struct pack_objects_args po_args = {NULL};
 	int geometric_factor = 0;
 	int write_midx = 0;

t/t7700-repack.sh

@@ -417,4 +417,22 @@ test_expect_success '-n skips updating server info' '
 	test_server_info_missing
 '
 
+test_expect_success 'repack.updateServerInfo=true updates server info' '
+	test_server_info_cleanup &&
+	git -C update-server-info -c repack.updateServerInfo=true repack &&
+	test_server_info_present
+'
+
+test_expect_success 'repack.updateServerInfo=false skips updating server info' '
+	test_server_info_cleanup &&
+	git -C update-server-info -c repack.updateServerInfo=false repack &&
+	test_server_info_missing
+'
+
+test_expect_success '-n overrides repack.updateServerInfo=true' '
+	test_server_info_cleanup &&
+	git -C update-server-info -c repack.updateServerInfo=true repack -n &&
+	test_server_info_missing
+'
+
 test_done