code: func (d *LocalDownloader) ListFilesInBuild(job string, buildNumber int, prefix string) ([]string, error) {
  	prefixDir, prefixFile := path.Split(prefix)
  	filesInDir, err := ioutil.ReadDir(path.Join(*localDataDir, fmt.Sprintf("%d", buildNumber), prefixDir))
  	if err != nil {
  		return nil, err
  	}
  	filesInBuild := []string{}
  	for _, file := range filesInDir {
  		if strings.HasPrefix(file.Name(), prefixFile) {
  			filesInBuild = append(filesInBuild, path.Join(prefixDir, file.Name()))
  		}
  	}
  	return filesInBuild, nil
  }
docs: // ListFilesInBuild returns the contents of the files with the specified prefix
  // for the test job at the given buildNumber.