copy/manifest.go
func isMultiImage(ctx context.Context, img types.UnparsedImage) (bool, error) {
	_, mt, err := img.Manifest(ctx)
	if err != nil {
		return false, err
	}
	return manifest.MIMETypeIsMultiImage(mt), nil
}
func isMultiImage(ctx context.Context, img types.UnparsedImage) (bool, error) {
	_, mt, err := img.Manifest(ctx)
	if err != nil {
		return false, err
	}
	return manifest.MIMETypeIsMultiImage(mt), nil
}
// isMultiImage returns true if img is a list of images