submodule: correct remote name with fetch

The code fetches the submodules remote based on the superproject remote name
instead of the submodule remote name[1].

Instead of grabbing the default remote of the superproject repository, ask
the default remote of the submodule we are going to run 'git fetch' in.

1. https://lore.kernel.org/git/ZJR5SPDj4Wt_gmRO@pweza/

Signed-off-by: Daniel Black <daniel@mariadb.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/submodule--helper.c

@@ -2333,7 +2333,14 @@ static int fetch_in_submodule(const char *module_path, int depth, int quiet,
 		strvec_pushf(&cp.args, "--depth=%d", depth);
 	if (oid) {
 		char *hex = oid_to_hex(oid);
-		char *remote = get_default_remote();
+		char *remote;
+		int code;
+
+		code = get_default_remote_submodule(module_path, &remote);
+		if (code) {
+			child_process_clear(&cp);
+			return code;
+		}
 
 		strvec_pushl(&cp.args, remote, hex, NULL);
 		free(remote);

t/t5572-pull-submodule.sh

@@ -230,6 +230,7 @@ test_expect_success 'branch has no merge base with remote-tracking counterpart'
 
 	test_create_repo a-submodule &&
 	test_commit -C a-submodule foo &&
+	test_commit -C a-submodule bar &&
 
 	test_create_repo parent &&
 	git -C parent submodule add "$(pwd)/a-submodule" &&
@@ -246,4 +247,23 @@ test_expect_success 'branch has no merge base with remote-tracking counterpart'
 	git -C child pull --recurse-submodules --rebase
 '
 
+test_expect_success 'fetch submodule remote of different name from superproject' '
+	git -C child remote rename origin o1 &&
+	git -C child submodule update --init &&
+
+	# Needs to create unreachable commit from current master branch.
+	git -C a-submodule checkout -b newmain HEAD^ &&
+	test_commit -C a-submodule echo &&
+	test_commit -C a-submodule moreecho &&
+	subc=$(git -C a-submodule rev-parse --short HEAD) &&
+
+	git -C parent/a-submodule fetch &&
+	git -C parent/a-submodule checkout "$subc" &&
+	git -C parent commit -m "update submodule" a-submodule &&
+	git -C a-submodule reset --hard HEAD^^ &&
+
+	git -C child pull --no-recurse-submodules &&
+	git -C child submodule update
+'
+
 test_done