/**
  * Returns diff of the changeset
  *
  * @return string
  * @throws Exception
  */
 public function getDiff()
 {
     /** @var \Github\Api\PullRequest $api */
     $api = $this->client->api('pull_request');
     $this->client->setHeaders(array('Accept' => sprintf('application/vnd.github.%s.diff', $this->client->getOption('api_version'))));
     $diff = $api->show($this->user, $this->repo, $this->pull);
     return $diff;
 }