Angular: force angular rerender

http://angularjs.org/

HTML

<script src="http://code.angularjs.org/angular-1.0.0rc8.js"></script>
<script src="http://code.jquery.com/jquery-1.7.2.min.js"></script>
<div ng-controller="MyCtrl">
    <div>{{message}}</div>
    <button ng-click="login()">Login</button>
</div>

JavaScript

var myApp = angular.module('myApp',[]);

//myApp.directive('myDirective', function() {});
//myApp.factory('myService', function() {});

function MyCtrl($rootScope, $scope) {
    if($rootScope.user) { // logged
        $scope.message = $http(...); // read some content from server
    } else {
        $scope.message = $http(...); // read some other content from server
    }
    $scope.login = function() {
        $rootScope.user = $http(...); // try login
    }
}