Edit in JSFiddle

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

testapp.controller('parentController', ['$scope', '$window',function($scope, $window) {
    $scope.primary1Label = 'Prime1';
    $scope.onPrimary1Click = function() {
        $window.alert('Primary 1 clicked');
    }        
}]);

testapp.directive('primary', function() {
    return {
        restrict: 'C',
        link: function(scope, element, attrs) {
            element.addClass('btn btn-primary');
        }
    }
});
    
testapp.directive('secondary', function() {
    return {
        restrict: 'C',
        link: function(scope, element, attrs) {
            element.addClass('btn');
        }
    }
});    

testapp.directive('buttonBar', function() {
    return {
        restrict: 'EA',
        template: '<div class="span4 well clearfix"><div class="primary-block pull-right"></div><div class="secondary-block"></div><div class="transcluded" ng-transclude></div></div>',
        replace: true,
        transclude: true,
        link: function(scope, element, attrs) {
            var primaryBlock = element.find('div.primary-block');
            var secondaryBlock = element.find('div.secondary-block');
            var transcludedBlock = element.find('div.transcluded');
            var transcludedButtons = transcludedBlock.children().filter(':button');
            angular.forEach(transcludedButtons, function(elem) {
                if (angular.element(elem).hasClass('primary')) {
                    primaryBlock.append(elem);
                } else if (angular.element(elem).hasClass('secondary')) {
                    secondaryBlock.append(elem);
                }
            });
            transcludedBlock.remove();
        }
    };
});

<div ng-controller="parentController">    
    <button-bar>
        <button class="primary" ng-click="onPrimary1Click()">{{primary1Label}}</button>
        <button class="primary">Primary2</button>
        <button class="secondary">Secondary1</button>
    </button-bar>
</div>

.primary, .secondary {
    margin-left: 5px;
    margin-right: 5px;
}