Merge branch 'js/mingw-is-hidden-test-fix'

A Windows-specific test element has been made more robust against
misuse from both user's environment and programmer's errors.

* js/mingw-is-hidden-test-fix:
  t: restrict `is_hidden` to be called only on Windows
  mingw: make test_path_is_hidden more robust
  t: consolidate the `is_hidden` functions

t/test-lib-functions.sh

@@ -1551,3 +1551,13 @@ test_bitmap_traversal () {
 	test_cmp "$1.normalized" "$2.normalized" &&
 	rm -f "$1.normalized" "$2.normalized"
 }
+
+# Tests for the hidden file attribute on Windows
+test_path_is_hidden () {
+	test_have_prereq MINGW ||
+	BUG "test_path_is_hidden can only be used on Windows"
+
+	# Use the output of `attrib`, ignore the absolute path
+	case "$("$SYSTEMROOT"/system32/attrib "$1")" in *H*?:*) return 0;; esac
+	return 1
+}