code: async function getPrFiles(prNo) {
    logger.debug({ prNo }, 'getPrFiles');
    const diff = (await api.get(
      `/2.0/repositories/${config.repository}/pullrequests/${prNo}/diff`,
      { json: false }
    )).body;
    const files = parseDiff(diff).map(file => file.to);
    return files;
  }
docs: Return a list of all modified files in a PR