Merge branch 'jt/ref-transaction-abort-fix' into next

A ref transaction corner case fix.

* jt/ref-transaction-abort-fix:
  builtin/fetch: avoid aborting closed reference transaction

Author: gitster

builtin/fetch.c

@@ -1844,8 +1844,15 @@ static int do_fetch(struct transport *transport,
 			goto cleanup;
 
 		retcode = ref_transaction_commit(transaction, &err);
-		if (retcode)
+		if (retcode) {
+			/*
+			 * Explicitly handle transaction cleanup to avoid
+			 * aborting an already closed transaction.
+			 */
+			ref_transaction_free(transaction);
+			transaction = NULL;
 			goto cleanup;
+		}
 	}
 
 	commit_fetch_head(&fetch_head);

t/t5510-fetch.sh

@@ -554,6 +554,19 @@ test_expect_success 'fetch --atomic --append appends to FETCH_HEAD' '
 	test_cmp expected atomic/.git/FETCH_HEAD
 '
 
+test_expect_success REFFILES 'fetch --atomic fails transaction if reference locked' '
+	test_when_finished "rm -rf upstream repo" &&
+
+	git init upstream &&
+	git -C upstream commit --allow-empty -m 1 &&
+	git -C upstream switch -c foobar &&
+	git clone --mirror upstream repo &&
+	git -C upstream commit --allow-empty -m 2 &&
+	touch repo/refs/heads/foobar.lock &&
+
+	test_must_fail git -C repo fetch --atomic origin
+'
+
 test_expect_success '--refmap="" ignores configured refspec' '
 	cd "$TRASH_DIRECTORY" &&
 	git clone "$D" remote-refs &&