tests: use 'test_must_be_empty' instead of 'test_cmp <empty> <out>'

diff --git a/t/t4060-diff-submodule-option-diff-format.sh b/t/t4060-diff-submodule-option-diff-format.sh
index 6fc3da8bd259e14f2736a35c8907215558014243..60c8dc75a99dbefba5e1f1d6f26449992b4f6f10 100755 (executable)
--- a/t/t4060-diff-submodule-option-diff-format.sh
+++ b/t/t4060-diff-submodule-option-diff-format.sh
@@ -392,9 +392,7 @@ test_expect_success 'typechanged submodule(blob->submodule)' '
 commit_file sm1 &&
 test_expect_success 'submodule is up to date' '
        git diff-index -p --submodule=diff HEAD >actual &&
-       cat >expected <<-EOF &&
-       EOF
-       test_cmp expected actual
+       test_must_be_empty actual
 '
 
 test_expect_success 'submodule contains untracked content' '