code: func NewTar(w io.Writer, targetDir string) *Tar {
  	return &Tar{
  		target:             targetDir,
  		dest:               w,
  		hardLinks:          make(map[uint64]string),
  		IncludePermissions: true,
  		IncludeOwners:      false,
  		OwnerMappingFunc:   defaultMappingFunc,
  		GroupMappingFunc:   defaultMappingFunc,
  	}
  }
docs: // NewTar returns a Tar ready to write the contents of targetDir to w.