refactor: do not store intermediate lists

    match the given collector's match criteria. If the collector has the

    recurse flag enabled, will also recursively descend into child folders.

    """

    matches = []

    parent_paths = parent_paths or []

    def _walk(target_dir, extra_file_collector, job_working_directory, matchable, parent_paths):

        directory = discover_target_directory(target_dir, job_working_directory)

        if os.path.isdir(directory):

            for filename in os.listdir(directory):

                        new_parent_paths = parent_paths[:]

                        new_parent_paths.append(filename)

                        # The current directory is already validated, so use that as the next job_working_directory when recursing

                    matches.extend(walk_over_extra_files(

                        yield from _walk(

                            filename, extra_file_collector, directory, matchable, parent_paths=new_parent_paths

                    ))

                        )

                else:

                    match = extra_file_collector.match(matchable, filename, path=path, parent_paths=parent_paths)

                    if match:

                    matches.append(match)

                        yield match

    for match in extra_file_collector.sort(matches):

    for match in extra_file_collector.sort(

        _walk(target_dir, extra_file_collector, job_working_directory, matchable, parent_paths)

    ):

        yield match