remote: resolve "simple" @{push} when pushing to another remote

With push.default left at "simple", a branch whose upstream is on one
remote and whose push remote is another gets pushed by "git push" to a
branch of the same name on the push remote. But @{push} for that
branch fails with "cannot resolve 'simple' push to a single
destination". As a result "git status" shows the "git push" hint under
the comparison with the upstream, even though "git push" goes
elsewhere, and leaves out the comparison with the push branch when
status.compareBranches asks for it.

"git push" learned to handle "simple" this way in ed2b18292b (push:
change `simple` to accommodate triangular workflows, 2013-06-19). When
@{push} was added in e291c75a95 (remote.c: add branch_get_push,
2015-05-21), its "simple" case only covered pushing back to the remote
the branch is fetched from, where the upstream must have the same name.

Make @{push} follow "git push". When the push remote is not the remote
of the branch, resolve to the branch of the same name on the push
remote, as "current" does.

The test added in 9bf9eed093 (remote: fix leak in branch_get_push_1()
with invalid "simple" config, 2026-01-19) relied on a different push
remote being invalid for "simple". Use an upstream with a different
name on the same remote instead, so that it still exercises the error
path.

Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

remote.c

@@ -1972,16 +1972,19 @@ static char *branch_get_push_simple(struct repository *repo,
 				    struct branch *branch,
 				    struct strbuf *err)
 {
-	const char *up;
+	const char *up = NULL;
 	char *cur;
 
-	up = branch_get_upstream(branch, err);
-	if (!up)
-		return NULL;
+	if (!strcmp(remote->name,
+		    remotes_remote_for_branch(repo->remote_state, branch, NULL))) {
+		up = branch_get_upstream(branch, err);
+		if (!up)
+			return NULL;
+	}
 	cur = tracking_for_push_dest(repo, remote, branch->refname, err);
 	if (!cur)
 		return NULL;
-	if (strcmp(cur, up)) {
+	if (up && strcmp(cur, up)) {
 		free(cur);
 		return error_buf(err,
 				 _("cannot resolve 'simple' push to a single destination"));

t/for-each-ref-tests.sh

@@ -1745,9 +1745,11 @@ test_expect_success ':remotename and :remoteref' '
 '
 
 test_expect_success '%(push) with an invalid push-simple config' '
+	test_when_finished "git config branch.main.merge refs/heads/main" &&
+	git config branch.main.merge refs/heads/not-main &&
 	echo "refs/heads/main " >expect &&
 	git -c push.default=simple \
-	    -c remote.pushdefault=myfork \
+	    -c remote.pushdefault=origin \
 	    for-each-ref \
 	    --format="%(refname) %(push)" refs/heads/main >actual &&
 	test_cmp expect actual

t/t1514-rev-parse-push.sh

@@ -39,7 +39,7 @@ test_expect_success '@{push} with default=simple' '
 	resolve main@{pUSh} refs/remotes/origin/main
 '
 
-test_expect_success 'triangular @{push} fails with default=simple' '
+test_expect_success '@{push} with default=simple fails when upstream has a different name' '
 	test_config push.default simple &&
 	test_must_fail git rev-parse topic@{push}
 '
@@ -60,6 +60,17 @@ test_expect_success '@{push} with pushremote defined' '
 	resolve topic@{push} refs/remotes/other/topic
 '
 
+test_expect_success 'triangular @{push} with default=simple and remote.pushdefault' '
+	test_config push.default simple &&
+	test_config remote.pushdefault other &&
+	test_when_finished "git checkout main" &&
+	git checkout topic &&
+	test_commit simple-triangular &&
+	git push &&
+	resolve topic@{push} refs/remotes/other/topic &&
+	test_cmp_rev topic topic@{push}
+'
+
 test_expect_success '@{p} is short for @{push}' '
 	test_config push.default current &&
 	test_config branch.topic.pushremote other &&