index-pack: run setup_git_directory_gently() sooner

index-pack already runs a repository search unconditionally; running
such a search earlier is not risky and ensures GIT_DIR will be set
correctly if the configuration needs to be accessed from
run_builtin().

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/index-pack.c

@@ -880,12 +880,10 @@ int cmd_index_pack(int argc, const char **argv, const char *prefix)
 	char *index_name_buf = NULL, *keep_name_buf = NULL;
 	struct pack_idx_entry **idx_objects;
 	unsigned char pack_sha1[20];
-	int nongit;
 
 	if (argc == 2 && !strcmp(argv[1], "-h"))
 		usage(index_pack_usage);
 
-	prefix = setup_git_directory_gently(&nongit);
 	git_config(git_index_pack_config, NULL);
 	if (prefix && chdir(prefix))
 		die("Cannot come back to cwd");

git.c

@@ -339,7 +339,7 @@ static void handle_internal_command(int argc, const char **argv)
 		{ "grep", cmd_grep, RUN_SETUP_GENTLY },
 		{ "hash-object", cmd_hash_object },
 		{ "help", cmd_help },
-		{ "index-pack", cmd_index_pack },
+		{ "index-pack", cmd_index_pack, RUN_SETUP_GENTLY },
 		{ "init", cmd_init_db },
 		{ "init-db", cmd_init_db },
 		{ "log", cmd_log, RUN_SETUP | USE_PAGER },