code: function getDiffForPR(pr) {
    print(['Get diff for PR ', clc.yellow.bold(`${pr.head.user.login}/${pr.head.repo.name}#${pr.number}`)], debug);
    return new Promise((resolve) => {
      github.repos.compareCommits({
        user: pr.head.user.login,
        repo: pr.head.repo.name,
        head: pr.head.ref,
        base: pr.base.ref
      }, (err, diff) => {
        if (err && debug) {
          print(['Error fetching diffs for PR ', clc.red.bold`${pr.head.user.login}/${pr.head.repo.name}#${pr.number}`], debug);
        }
        diff.user = pr.head.user.login;
        diff.repo = pr.head.repo.name;
        diff.title = pr.title;
        diff.number = pr.number;
        diff.link = pr._links.html.href;
        diff.createdAt = pr.created_at;
        diff.createdAt = pr.updated_at;
        diff.labels = pr.labels;
        return resolve(extractDiffData(diff));
      });
    });
  }
docs: Fetch the diff for a single pull-request
  @param  {Object}  pr Pull-request metadata
  @return {Promise}    Resolves to an array of labels