allow override of rendering after a collection sort

docs/marionette.collectionview.md

@@ -48,6 +48,7 @@ will provide features such as `onShow` callbacks, etc. Please see
 * [CollectionView: Automatic Rendering](#collectionview-automatic-rendering)
 * [CollectionView: Re-render Collection](#collectionview-re-render-collection)
 * [CollectionView's attachHtml](#collectionviews-attachhtml)
+* [CollectionView's resortView](#collectionviews-resortview)
 * [CollectionView's children](#collectionviews-children)
 * [CollectionView destroy](#collectionview-destroy)
 
@@ -707,6 +708,25 @@ Overrides of `attachHtml` that don't take into account the element
 buffer will work fine, but won't take advantage of the 60x performance
 increase the buffer provides.
 
+## CollectionView's resortView
+
+By default the `CollectionView` will maintain the order of its `collection`
+in the DOM, however on occasions the view may need to re-render to make this
+possible, for example if you were to change the comparator on the collection.
+By default `CollectionView` will call `render` when this happens but there are
+cases where this may not be suitable, for instance when sorting the `children`
+in a `CompositeView`, in this instance you want to only render the internal
+collection.
+
+```js
+var cv = new Marionette.CollectionView({
+  collection: someCollection,
+  resortView: function() {
+    // provide custom logic for rendering after sorting the collection
+  }
+});
+```
+
 ## CollectionView's children
 
 The CollectionView uses [Backbone.BabySitter](https://github.com/marionettejs/backbone.babysitter)

src/marionette.collectionview.js

@@ -118,17 +118,25 @@ Marionette.CollectionView = Marionette.View.extend({
     return this;
   },
 
+  // Render view after sorting. Override this method to
+  // change how the view renders after a `sort` on the collection.
+  // An example of this would be to only `renderChildren` in a `CompositeView`
+  // rather than the full view.
+  resortView: function() {
+    this.render();
+  },
+
   // Internal method. This checks for any changes in the order of the collection.
   // If the index of any view doesn't match, it will render.
-  _sortViews: function(){
+  _sortViews: function() {
     // check for any changes in sort order of views
     var orderChanged = this.collection.find(function(item, index){
       var view = this.children.findByModel(item);
       return view && view._index !== index;
     }, this);
 
     if (orderChanged) {
-      this.render();
+      this.resortView();
     }
   },