title: Mongoose update: obtaining pushed subdocument's _id
body: <p>Having the following <code>update</code> <em>query</em>:</p>
  
  <pre><code>var template = {name:'my_name', ...};
  ApplicationModel.update({
          _id: idApplication,
          'templates.name': { '$ne': template.name }
      },
      {
          $push: { templates: template }
      }, function(err, raw) {
            if (err) {
                return callback(err);
            }
            ...
            callback();
      });
  </code></pre>
  
  <p>Inside <code>ApplicationModel</code> there is an array called <code>templates</code> where I push <code>template</code> objects and <strong>Mongoose</strong> assigns each of these objects automatically an <code>_id</code>.</p>
  
  <p>Is there a way to obtain this <code>_id</code> in the query's callback function?</p>