Merge branch 'jc/push-delete-nothing'

"git push $there --delete ''" should have been diagnosed as an
error, but instead turned into a matching push, which has been
corrected.

* jc/push-delete-nothing:
  push: do not turn --delete '' into a matching push

builtin/push.c

@@ -115,7 +115,7 @@ static void set_refspecs(const char **refs, int nr, const char *repo)
 			else
 				refspec_appendf(&rs, "refs/tags/%s", ref);
 		} else if (deleterefs) {
-			if (strchr(ref, ':'))
+			if (strchr(ref, ':') || !*ref)
 				die(_("--delete only accepts plain target ref names"));
 			refspec_appendf(&rs, ":%s", ref);
 		} else if (!strchr(ref, ':')) {

t/t5516-fetch-push.sh

@@ -820,6 +820,11 @@ test_expect_success 'push --delete refuses src:dest refspecs' '
 	test_must_fail git push testrepo --delete main:foo
 '
 
+test_expect_success 'push --delete refuses empty string' '
+	mk_test testrepo heads/master &&
+	test_must_fail git push testrepo --delete ""
+'
+
 test_expect_success 'warn on push to HEAD of non-bare repository' '
 	mk_test testrepo heads/main &&
 	(