public function show($username, $repository, $path = null, $reference = null)
    {
        $url = '/repos/'.rawurlencode($username).'/'.rawurlencode($repository).'/contents';
        if (null !== $path) {
            $url .= '/'.rawurlencode($path);
        }

        return $this->get($url, [
            'ref' => $reference,
        ]);
    }