readlink method
Reads the target of a symbolic link.
Implementation
Future<String> readlink(String path) async {
final reply = await _sendReadLink(path);
if (reply is SftpNamePacket) return reply.names.first.filename;
if (reply is! SftpStatusPacket) throw SftpError('Unexpected reply');
throw SftpStatusError.fromStatus(reply);
}