public function performMerge(string $base, string $head, string $commitMessage = null): array
    {
        return $this->getApi()->request($this->getApi()->sprintf('/repos/:owner/:repo/merges',
            $this->getRepositories()->getOwner(), $this->getRepositories()->getRepo()), Request::METHOD_POST, [
                'base'           => $base,
                'head'           => $head,
                'commit_message' => $commitMessage
            ]);
    }