Don't show comment form if user not logged in

app/assets/javascripts/backbone/templates/comments/index.jst.hbs

@@ -1,6 +1,7 @@
 <ul class="comments">
 </ul>
 
+{{#if show_form}}
 <form id="new-comment">
   <p>
     <textarea type="text" name="body" id="comment-body"></textarea>
@@ -8,3 +9,6 @@
 
   <input type="submit" value="Post">
 </form>
+{{else}}
+  <div>You need to sign in to create a comment.</div>
+{{/if}}

app/assets/javascripts/backbone/views/comments/comments_index.js.coffee

@@ -10,8 +10,11 @@ class AsciiIo.Views.CommentsIndex extends Backbone.View
     @collection.on('reset', @render, this)
     @collection.on('add', @render, this)
 
+    @current_user = AsciiIo.current_user
+
   render: ->
-    $(@el).html @template
+    $(@el).html @template( show_form: @current_user )
+
     $comments = this.$('.comments')
 
     @collection.each (comment) ->