t3203: test 'detached at' after checkout --detach

This currently fails: the output is 'HEAD detached at HEAD'.

Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t3203-branch-output.sh

@@ -106,6 +106,19 @@ EOF
 	test_i18ncmp expect actual
 '
 
+test_expect_failure 'git branch shows detached HEAD properly after checkout --detach' '
+	git checkout master &&
+	cat >expect <<EOF &&
+* (HEAD detached at $(git rev-parse --short HEAD^0))
+  branch-one
+  branch-two
+  master
+EOF
+	git checkout --detach &&
+	git branch >actual &&
+	test_i18ncmp expect actual
+'
+
 test_expect_success 'git branch shows detached HEAD properly after moving' '
 	cat >expect <<EOF &&
 * (HEAD detached from $(git rev-parse --short HEAD))