func (fi *FileInfo) TierFreeVersionID() string {
	return fi.Metadata[ReservedMetadataPrefixLower+tierFVID]
}

// SetTierFreeVersion sets fi as a free-version. This method is used by
// lower layers to indicate a free-version.
func (fi *FileInfo) SetTierFreeVersion() {
	if fi.Metadata == nil {
		fi.Metadata = make(map[string]string)
	}
	fi.Metadata[ReservedMetadataPrefixLower+tierFVMarker] = ""
}