name-rev: make dedicated --annotate-stdin --name-only test

The previous commit split the `--name-only` handling:

1. `--annotate-stdin`: uses the new `struct command`
2. The rest: uses `struct name_ref_data`

But there is no dedicated test for the option combination in (1). That
means that the following tests will fail if you neglect to set
`command.u.name_only` properly:

    name-rev --annotate-stdin works with commitGraph
    name-rev --annotate-stdin works with non-monotonic timestamps

even though it has nothing to do with what these tests are supposed
to test.

Let’s add another regression test now that it is relevant.

Signed-off-by: Kristoffer Haugsbakk <code@khaugsbakk.name>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t6120-describe.sh

@@ -298,6 +298,20 @@ test_expect_success 'name-rev --annotate-stdin' '
 	test_cmp expect actual
 '
 
+test_expect_success 'name-rev --annotate-stdin --name-only' '
+	>expect.unsorted &&
+	for rev in $(git rev-list --all)
+	do
+		name=$(git name-rev --name-only $rev) &&
+		echo "$name" >>expect.unsorted || return 1
+	done &&
+	sort <expect.unsorted >expect &&
+	git name-rev --annotate-stdin --name-only \
+		<list >actual.unsorted &&
+	sort <actual.unsorted >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'name-rev --stdin deprecated' '
 	git rev-list --all >list &&
 	if ! test_have_prereq WITH_BREAKING_CHANGES