Show note if layer branch hasn't been indexed

For newly added layers it may not be immediately obvious that you have
to wait for it to be indexed (since the update script is usually run on
a scheduled basis). If the layer branch hasn't been indexed, add a note
mentioning this.

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>

templates/layerindex/detail.html

@@ -167,6 +167,11 @@
             </div>  <!-- end of row-fluid -->
         </div> <!-- end of container-fluid -->
 
+        {% if not layerbranch.vcs_last_commit %}
+        <div class="alert alert-info">
+            <b>Note:</b> The content of this layer on branch {{ url_branch }} has not yet been indexed. Indexing should take place within a few hours.
+        </div>
+        {% endif %}
 
         <ul class="nav nav-tabs" id="layertabbar">
             {% if layerbranch.recipe_set.count > 0 %}