submodule: don't add submodule as odb for push

In push_submodule(), because we do not actually need access to objects
in the submodule, do not invoke add_submodule_odb().
(for_each_remote_ref_submodule() does not require access to those
objects, and the actual push is done by spawning another process,
which handles object access by itself.)

This code of push_submodule() is exercised in t5531 and continues
to work, showing that the submodule odbc is not needed.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

submodule.c

@@ -1023,9 +1023,6 @@ static int push_submodule(const char *path,
 			  const struct string_list *push_options,
 			  int dry_run)
 {
-	if (add_submodule_odb(path))
-		return 1;
-
 	if (for_each_remote_ref_submodule(path, has_remote, NULL) > 0) {
 		struct child_process cp = CHILD_PROCESS_INIT;
 		argv_array_push(&cp.args, "push");