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>
diff --git a/git.c b/git.c
index eaf6e7f..9824068 100644
--- a/git.c
+++ b/git.c
@@ -339,7 +339,7 @@
 		{ "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 },