public function push($target, $ref, $targetBranch = 'master', $force = true)
    {
        $cmd = [
            'git push -q',
            sprintf('https://%s@github.com/%s', $this->token, $target),
            sprintf('%s:%s', $ref, $targetBranch)
        ];

        if ($force) {
            $cmd[] = '--force';
        }

        return $this->shell->execute(implode(' ' , $cmd));
    }