code: func renameExpired(preparedExpiration time.Duration) error {
  	if err := pkgPod.WalkPods(getDataDir(), pkgPod.IncludePreparedDir, func(p *pkgPod.Pod) {
  		st := &syscall.Stat_t{}
  		pp := p.Path()
  		if err := syscall.Lstat(pp, st); err != nil {
  			if err != syscall.ENOENT {
  				stderr.PrintE(fmt.Sprintf("unable to stat %q, ignoring", pp), err)
  			}
  			return
  		}
  
  		if expiration := time.Unix(st.Ctim.Unix()).Add(preparedExpiration); time.Now().After(expiration) {
  			stderr.Printf("moving expired prepared pod %q to garbage", p.UUID)
  			if err := p.ToGarbage(); err != nil && err != os.ErrNotExist {
  				stderr.PrintE("rename error", err)
  			}
  		}
  	}); err != nil {
  		return err
  	}
  	return nil
  }
docs: // renameExpired renames expired prepared pods to the garbage directory