added a SymfonyBridgesExtension

For now, it allows the Twig extension to register the Routing Twig extension:

$app = new Application();
$app->register(new SymfonyBridgesExtension(), array(
    'symfony_bridges.class_path' => '...',
));
$app->register(new UrlGeneratorExtension());
$app->register(new SessionExtension());
$app->register(new TwigExtension(), array(...));

You can now use {{ path() }} in templates to generate URLs.

The order of registration of the extensions is significant.

src/Silex/Extension/SymfonyBridgesExtension.php

+<?php
+
+/*
+ * This file is part of the Silex framework.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Silex\Extension;
+
+use Silex\Application;
+use Silex\ExtensionInterface;
+
+use Symfony\Component\Routing\Generator\UrlGenerator;
+
+class SymfonyBridgesExtension implements ExtensionInterface
+{
+    public function register(Application $app)
+    {
+        $app['symfony_bridges'] = true;
+
+        if (isset($app['symfony_bridges.class_path'])) {
+            $app['autoloader']->registerNamespace('Symfony\\Bridge', $app['symfony_bridges.class_path']);
+        }
+    }
+}

src/Silex/Extension/TwigExtension.php

@@ -13,6 +13,7 @@ namespace Silex\Extension;
 
 use Silex\Application;
 use Silex\ExtensionInterface;
+use Symfony\Bridge\Twig\Extension\RoutingExtension;
 
 class TwigExtension implements ExtensionInterface
 {
@@ -25,6 +26,10 @@ class TwigExtension implements ExtensionInterface
                 $app['twig.configure']($twig);
             }
 
+            if (isset($app['url_generator']) && isset($app['symfony_bridges'])) {
+                $twig->addExtension(new RoutingExtension($app['url_generator']));
+            }
+
             return $twig;
         });