grep: run setup_git_directory_gently() sooner

git grep already runs a repository search unconditionally,
even when the --no-index option is supplied; running such a
search earlier is not very risky.

Just like with shortlog, without this change, the
“[pager] grep” configuration is not respected at all.

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>

git.c

@@ -336,7 +336,7 @@ static void handle_internal_command(int argc, const char **argv)
 		{ "fsck-objects", cmd_fsck, RUN_SETUP },
 		{ "gc", cmd_gc, RUN_SETUP },
 		{ "get-tar-commit-id", cmd_get_tar_commit_id },
-		{ "grep", cmd_grep },
+		{ "grep", cmd_grep, RUN_SETUP_GENTLY },
 		{ "hash-object", cmd_hash_object },
 		{ "help", cmd_help },
 		{ "index-pack", cmd_index_pack },