1. use Decoreate:
angular.module('jsbin', ['ui.bootstrap']).config(Decorate);

Decorate.inject = ['$provide'];

function Decorate($provide) {

    $provide.decorator('alertDirective', function ($delegate) {

        var directive = $delegate[0];
        directive.templateUrl = "alertOverride.tpl.html";
        return $delegate;
    });
}

//2. use run and $templateCache:
angular.module("template/alert/alert.html", []).run(["$templateCache",
 function ($templateCache) {

  $templateCache.put("template/alert/alert.html",
   "<div class='alert' ng-class='type && "alert-" + type'>n" +
   " <button ng-show='closeable' type='button' class='close' ng-click='close()'>Close</button>n" +
   "  <div ng-transclude></div>n" +
   "</div>");
}]);