call jgitenv.setup() before any jgit call

jgit auth

object jgitenv {
  def setup() {
    val jschConfigSessionFactory = new JschConfigSessionFactory() {
      override def createDefaultJSch(fs:FS) = {
        val jsch = new JSch();
        try {
          jsch.addIdentity("..\\id_rsa"); //_.pub must exist
          jsch.setKnownHosts("..\\known_hosts");

        } catch {
          case e: JSchException => {
            e.printStackTrace();
          }
        }
        jsch
      }
      override def configure(host: OpenSshConfig.Host, session: Session) {
        session.setConfig("StrictHostKeyChecking", "no");
        //session.setConfig("IdentityFile", "..\\id_rsa")
        session.setConfig("PreferredAuthentications", "publickey");
        //session.setConfig("PreferredAuthentications", "gssapi-with-mic");
        //session.setPassword("12345678")
      }
        }
        SshSessionFactory.setInstance(jschConfigSessionFactory);
  }
}

more reference:
http://dev.vaadin.com/svn/incubator/Arvue/VersionControl/src/org/nest/versioncontrol/authentication/GitSshSessionFactory.java
https://gist.github.com/quidryan/5449155