protected static function simpleMerge(string $base, string $remote, string $local)
    {
        // Skip complex merging if there is nothing to do.
        if ($base == $remote) {
            return $local;
        }
        if ($base == $local) {
            return $remote;
        }
        if ($remote == $local) {
            return $remote;
        }
        // Return nothing and let sub-classes deal with it.
        return null;
    }