code: async function getPrFiles(prNo) {
    logger.debug({ prNo }, 'getPrFiles');
    if (!prNo) {
      return [];
    }
    const files = (await get(
      `repos/${config.parentRepo || config.repository}/pulls/${prNo}/files`
    )).body;
    return files.map(f => f.filename);
  }
docs: Return a list of all modified files in a PR