t7406: avoid using test_must_fail for commands other than git

diff --git a/t/t7406-submodule-update.sh b/t/t7406-submodule-update.sh
index 24aa732312824ab21a712e1b88e3d6098d9aca57..815b60cb593fbb2695b6f0957cfe02b84922bd2f 100755 (executable)
--- a/t/t7406-submodule-update.sh
+++ b/t/t7406-submodule-update.sh
@@ -606,7 +606,7 @@ test_expect_success 'submodule update - update=none in .git/config but --checkou
         git diff --name-only >out &&
         ! grep ^submodule$ out &&
         (cd submodule &&
-         test_must_fail compare_head
+         ! compare_head
         ) &&
         git config --unset submodule.submodule.update
        )