docker/tarfile/dest.go
func (d *Destination) sendSymlink(path string, target string) error {
	hdr, err := tar.FileInfoHeader(&tarFI{path: path, size: 0, isSymlink: true}, target)
	if err != nil {
		return nil
	}
	logrus.Debugf("Sending as tar link %s -> %s", path, target)
	return d.tar.WriteHeader(hdr)
}
func (d *Destination) sendSymlink(path string, target string) error {
	hdr, err := tar.FileInfoHeader(&tarFI{path: path, size: 0, isSymlink: true}, target)
	if err != nil {
		return nil
	}
	logrus.Debugf("Sending as tar link %s -> %s", path, target)
	return d.tar.WriteHeader(hdr)
}
// sendSymlink sends a symlink into the tar stream.