Merge branch 'jc/maint-diff-q-filter'

* jc/maint-diff-q-filter:
  diff --quiet: disable optimization when --diff-filter=X is used

t/t4040-whitespace-status.sh

@@ -60,4 +60,11 @@ test_expect_success 'diff-files -b -p --exit-code' '
 	git diff-files -b -p --exit-code
 '
 
+test_expect_success 'diff-files --diff-filter --quiet' '
+	git reset --hard &&
+	rm a/d &&
+	echo x >>b/e &&
+	test_must_fail git diff-files --diff-filter=M --quiet
+'
+
 test_done