		`@@ -556,6 +556,10 @@`
		`if not subdirs:`
		`return []`
		`for subdir in subdirs:`
		`+ if subdir is None:`
		`+ # this should never happen, but better to skip`
		`+ # this than kill some backend process`
		`+ continue`
		`args += [option, subdir]`
		`return args`
		`cmd += subdirs('--add', add)`

		`@@ -44,11 +44,28 @@`
		`return sp.returncode`


		`+ def arg_parser_subdir_type(subdir):`
		`+ if not subdir:`
		`+ raise argparse.ArgumentTypeError("subdir can not be empty string")`
		`+ if '..' in subdir:`
		`+ raise argparse.ArgumentTypeError(`
		`+ "relative '..' in subdir name '{}'".format(subdir))`
		`+ if ' ' in subdir:`
		`+ raise argparse.ArgumentTypeError(`
		`+ "space character in subdir name '{}'".format(subdir))`
		`+ if '/' in subdir:`
		`+ raise argparse.ArgumentTypeError(`
		`+ "'/' in subdir name '{}', we support only single-level subdir "`
		`+ "for now".format(subdir))`
		`+ return subdir`
		`+`
		`+`
		`def get_arg_parser():`
		`parser = argparse.ArgumentParser()`
		`parser.add_argument('--delete', action='append', metavar='SUBDIR',`
		`- default=[])`
		`- parser.add_argument('--add', action='append', metavar='SUBDIR', default=[])`
		`+ default=[], type=arg_parser_subdir_type)`
		`+ parser.add_argument('--add', action='append', metavar='SUBDIR', default=[],`
		`+ type=arg_parser_subdir_type)`
		`parser.add_argument('--devel', action='store_true', default=False)`
		`parser.add_argument('--no-appstream-metadata', action='store_true',`
		`default=False)`

		`@@ -100,3 +100,24 @@`
		`# wouldn't be able to reference ../ locations`
		`assert updated['packages']['prunerepo']['xml:base'] == \`
		`'https://example.com/results/john/empty/fedora-rawhide-x86_64'`
		`+`
		`+ @pytest.mark.parametrize('add', [`
		`+ ["aaa", ''],`
		`+ ["File 1"],`
		`+ ["slash/in/path"],`
		`+ [".."],`
		`+ ])`
		`+ def test_copr_repo_subdir_validator(self, add, capfd):`
		`+ assert 0 == call_copr_repo('/some/dir', add=add)`
		`+ # not using capsys because pytest/issues/5997`
		`+ _, err = capfd.readouterr()`
		`+ assert 'copr-repo: error: argument' in err`
		`+`
		`+ @mock.patch("backend.helpers.subprocess.call")`
		`+ def test_copr_repo_subdir_none_doesnt_raise(self, call):`
		`+ """ check that None is skipped in add (or delete) """`
		`+ call.return_value = 0 # exit status 0`
		`+ assert True == call_copr_repo('/some/dir', add=['xxx', None])`
		`+ assert len(call.call_args_list) == 1`
		`+ call = call.call_args_list[0]`
		`+ assert call[0][0] == ['copr-repo', '/some/dir', '--add', 'xxx']`