t/lib-submodule-update.sh: clarify test

diff --git a/t/lib-submodule-update.sh b/t/lib-submodule-update.sh
index f39ec3095191da6c89695d44b78d9129965c4ec0..d7699046f6545be28d5c39c058d4ca9db9e93793 100755 (executable)
--- a/t/lib-submodule-update.sh
+++ b/t/lib-submodule-update.sh
@@ -657,6 +657,23 @@ test_submodule_recursing_with_args_common() {
                        test_submodule_content sub1 origin/add_sub1
                )
        '
+       test_expect_success "$command: submodule branch is not changed, detach HEAD instead" '
+               prolog &&
+               reset_work_tree_to_interested add_sub1 &&
+               (
+                       cd submodule_update &&
+                       git -C sub1 checkout -b keep_branch &&
+                       git -C sub1 rev-parse HEAD >expect &&
+                       git branch -t modify_sub1 origin/modify_sub1 &&
+                       $command modify_sub1 &&
+                       test_superproject_content origin/modify_sub1 &&
+                       test_submodule_content sub1 origin/modify_sub1 &&
+                       git -C sub1 rev-parse keep_branch >actual &&
+                       test_cmp expect actual &&
+                       test_must_fail git -C sub1 symbolic-ref HEAD
+               )
+       '
+
        # Replacing a tracked file with a submodule produces a checked out submodule
        test_expect_success "$command: replace tracked file with submodule checks out submodule" '
                prolog &&