docker/tarfile/dest.go
func (d *Destination) PutSignatures(ctx context.Context, signatures [][]byte) error {
	if len(signatures) != 0 {
		return errors.Errorf("Storing signatures for docker tar files is not supported")
	}
	return nil
}
func (d *Destination) PutSignatures(ctx context.Context, signatures [][]byte) error {
	if len(signatures) != 0 {
		return errors.Errorf("Storing signatures for docker tar files is not supported")
	}
	return nil
}
// PutSignatures adds the given signatures to the docker tarfile (currently not
// supported). MUST be called after PutManifest (signatures reference manifest
// contents)