def _prune_hash_result(hash_result):
    """Prunes a dict of {hash : [file_path, ...], ...} to just those entries
    that have >1 file_path."""
    keys = []
    for k in hash_result:
        if len(hash_result[k]) == 1:
            keys.append(k)
    for k in keys:
        del hash_result[k]
