return nil
	}
	// Binary search to find where dir starts and ends in the list
	// and then return that slice of the list.
	files := *f.files
	i := sortSearch(len(files), func(i int) bool {
		idir, _, _ := split(files[i].name)
		return idir >= dir
	})
	j := sortSearch(len(files), func(j int) bool {
		jdir, _, _ := split(files[j].name)
		return jdir > dir
	})
	return files[i:j]
}