title: How to define default date values in Symfony2 routes?
body: <p>If I want to create a route, where the year, month and date are variables, how can I define that if these variables are empty, the current date shall be taken?</p>
  
  <p>E.g. like this (doesn't work for sure...)</p>
  
  <pre><code>blog:
      path:      /blog/{year}/{month}/{day}
      defaults:  { _controller: AcmeBlogBundle:Blog:index,
                      year:  current_year,
                      month: current_month
                      day:   current_day
                 }
  </code></pre>
  
  <p>I thought about defining two different routes, like this</p>
  
  <pre><code>blog_current_day:
      path:      /blog
      defaults:  { _controller: AcmeBlogBundle:Blog:index }
  
  blog:
      path:      /blog/{year}/{month}/{day}
      defaults:  { _controller: AcmeBlogBundle:Blog:index }
  </code></pre>
  
  <p>But if I then call <code>blog_current_day</code> my controller</p>
  
  <pre><code>public function indexAction(Request $request, $year, $month, $day) {
      // ...
  }
  </code></pre>
  
  <p>will throw an exception because year, month and day are missing.</p>
  
  <p>Any suggestions?</p>