t5516: add test case for pushing remote refspecs

"git push remote-name" (that is, with no refspec given on the command
line) should push the refspecs in remote.remote-name.push. There is no
test case that checks this behavior in detached HEAD, so add one.

Signed-off-by: Glen Choo <chooglen@google.com>
Reviewed-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5516-fetch-push.sh

@@ -541,6 +541,15 @@ do
 
 done
 
+test_expect_success "push to remote with no explicit refspec and config remote.*.push = src:dest" '
+	mk_test testrepo heads/main &&
+	git checkout $the_first_commit &&
+	test_config remote.there.url testrepo &&
+	test_config remote.there.push refs/heads/main:refs/heads/main &&
+	git push there &&
+	check_push_result testrepo $the_commit heads/main
+'
+
 test_expect_success 'push with remote.pushdefault' '
 	mk_test up_repo heads/main &&
 	mk_test down_repo heads/main &&