can.Model "update" sends all instance attributes to server.

Hi Justin,

I am making a PUT request using can.Model functionality. When PUT request is sent to server it sends all the attributes along with the changed attribute.

-----code---

        var Test = can.Model({
            create:"POST http://localhost/evens",
            update:"PUT http://localhost/evens/{id}"
          
        },{});

  can.fixture("POST http://localhost/evens",
                     function(request, response, headers){
                    response({id:8},'','',{"Access-Control-Allow-Origin":"*"});
        })
  can.fixture("PUT http://localhost/evens/{id}",
                     function(request, response, headers){);
                    response({id:""},'','',{"Access-Control-Allow-Origin":"*"});
        })
        var shopping = new Test({name:"Tom",desc:"Lorem Ipsum"});
                shopping.save(function(saved) {
                saved.attr('name', 'Jenna');
                saved.save(); ///sends {id:8,name:'Jenna', desc:'Lorem Ipsum'} to server rather {name:'Jenna'}
          });
------code----

I would like to know is this the existing behavior or my implementation is wrong.

Best Regards,
Sushil J