tarball/tarball_src.go
func (*tarballImageSource) LayerInfosForCopy(ctx context.Context) ([]types.BlobInfo, error) {
	return nil, nil
}
func (*tarballImageSource) LayerInfosForCopy(ctx context.Context) ([]types.BlobInfo, error) {
	return nil, nil
}
// LayerInfosForCopy() returns updated layer info that should be used when reading, in preference to values in the manifest, if specified.