code: func evalBuildline(buildline string) (int64, error) {
  	matches := buildlineRE.FindStringSubmatch(buildline)
  
  	// +1 to make it more obvious that the whole string containing the info is also returned as matches[0].
  	if len(matches) < 1+1 {
  		return 0, fmt.Errorf("too few matches found in buildline: %s", buildline)
  	}
  
  	if len(matches) > 1+1 {
  		return 0, fmt.Errorf("too many matches found in buildline: %s", buildline)
  	}
  
  	syncedSize, err := strconv.ParseInt(matches[1], 10, 64)
  
  	if err != nil {
  		return 0, fmt.Errorf("%s in buildline: %s", err, buildline)
  	}
  
  	return syncedSize, nil
  }
docs: // evalBuildline gets the size that has already been synced out of the sync-line.