code: public Authentication getTransportAuthentication() {
          Authentication a = transportAuth; 
          if (a==null)    a = Jenkins.ANONYMOUS;
          return a;
      }
docs: Returns the identity of the client as determined at the CLI transport level.
  
  <p>
  When the CLI connection to the server is tunneled over HTTP, that HTTP connection
  can authenticate the client, just like any other HTTP connections to the server
  can authenticate the client. This method returns that information, if one is available.
  By generalizing it, this method returns the identity obtained at the transport-level authentication.
  
  <p>
  For example, imagine if the current {@link SecurityRealm} is doing Kerberos authentication,
  then this method can return a valid identity of the client.
  
  <p>
  If the transport doesn't do authentication, this method returns {@link jenkins.model.Jenkins#ANONYMOUS}.