title: Symfony Twig - get default _locale in twig
body: <p>I'm adding a language switcher on my website.</p>
  
  <p>my parameters are like this :</p>
  
  <pre><code>avc_coming_soon:
  resource: "@AVCComingSoonBundle/Controller/"
  type:     annotation
  prefix:   /{_locale}
  defaults:
      _locale: en
  requirements:
      _locale: |fr
  </code></pre>
  
  <p><code>en</code> is set by default</p>
  
  <p>In my twig, I did that: </p>
  
  <pre><code>&lt;div class="languages"&gt;
          &lt;ul class="lang-menu"&gt;
              &lt;li class="en"&gt;&lt;a href="{{ path(app.request.get('_route'), {'_locale': 'en' })  }}"&gt;&lt;img src="{{ asset('images/flag_en.gif') }}" alt="EN"&gt;&lt;/a&gt;&lt;/li&gt;
              &lt;li class="fr"&gt;&lt;a href="{{ path(app.request.get('_route'), {'_locale': 'fr'})  }}"&gt;&lt;img src="{{ asset('images/flag_fr.gif') }}" alt="FR"&gt;&lt;/a&gt;&lt;/li&gt;
          &lt;/ul&gt;
      &lt;/div&gt;
  </code></pre>
  
  <p>But when I click on 'English', my path become <code>www.mysite.com/en</code> or the good route is <code>www.mysite.com/</code> (without the <code>/en</code>) because in parameters, I have this :</p>
  
  <pre><code>defaults:
      _locale: en
  </code></pre>
  
  <p>How to get the default _locale in twig ?</p>
  
  <pre><code>{{ path(app.request.get('_route'), {'_locale': &lt;&lt;&lt;default&gt;&gt;&gt; })  }}
  </code></pre>
  
  <p>thank you :)</p>