func (d *dirImageDestination) PutManifest(ctx context.Context, manifest []byte) error {
	return ioutil.WriteFile(d.ref.manifestPath(), manifest, 0644)
}
func (d *dirImageDestination) PutManifest(ctx context.Context, manifest []byte) error {
	return ioutil.WriteFile(d.ref.manifestPath(), manifest, 0644)
}
// PutManifest writes manifest to the destination.
// FIXME? This should also receive a MIME type if known, to differentiate between schema versions.
// If the destination is in principle available, refuses this manifest type (e.g. it does not recognize the schema),
// but may accept a different manifest type, the returned error must be an ManifestTypeRejectedError.