code: func (fis FileInfoSums) SortBySums() {
  	dups := fis.GetDuplicatePaths()
  	if len(dups) > 0 {
  		sort.Sort(bySum{fis, dups})
  	} else {
  		sort.Sort(bySum{fis, nil})
  	}
  }
docs: // SortBySums sorts FileInfoSums content by sums.