code: func (fis FileInfoSums) GetDuplicatePaths() (dups FileInfoSums) {
  	seen := make(map[string]int, len(fis)) // allocate earl. no need to grow this map.
  	for i := range fis {
  		f := fis[i]
  		if _, ok := seen[f.Name()]; ok {
  			dups = append(dups, f)
  		} else {
  			seen[f.Name()] = 0
  		}
  	}
  	return dups
  }
docs: // GetDuplicatePaths returns a FileInfoSums with all duplicated paths.