protected function getHead()
    {
        $data = $this->head;

        if (preg_match('#last-updated: (.*)#', $data, $match)) {
            $data = str_replace($match[1], date('c', $this->lastchange), $data);
        }

        if ($this->transifexProject
            && preg_match_all(
                '#https://www.transifex.com/projects/p/.*/language/.*/#',
                $data,
                $match,
                PREG_OFFSET_CAPTURE
            )
        ) {
            $data = substr_replace(
                $data,
                sprintf(
                    'https://www.transifex.com/projects/p/%s/language/%s/',
                    $this->transifexProject,
                    $this->language
                ),
                $match[0][0][1],
                strlen($match[0][0][0])
            );
        }

        return $data;
    }