def _list_new_metadata(repository_path):
    """
    List the filenames of new and changed repository metadata files.

    :param FilePath repository_path: Location of repository to list repository
        metadata from.
    :param set existing_metadata: Filenames of existing metadata files.
    """
    return {"/".join(path.segmentsFrom(repository_path))
            for path in repository_path.child('repodata').walk()}