code: func fileInfo(file string) (*info, error) {
  	info := &info{file: file, Year: int64(time.Now().Year())}
  	cmd := exec.Command("git", "log", "--follow", "--find-renames=80", "--find-copies=80", "--pretty=format:%ai", "--", file)
  	err := doLines(cmd, func(line string) {
  		y, err := strconv.ParseInt(line[:4], 10, 64)
  		if err != nil {
  			fmt.Printf("cannot parse year: %q", line[:4])
  		}
  		if y < info.Year {
  			info.Year = y
  		}
  	})
  	return info, err
  }
docs: // fileInfo finds the lowest year in which the given file was committed.