[Bugfix] Use deregisterItem instead of registerItem on destroy

[Feature] Adding isDraggingDisabled flag to allow specifying a sortable-item to be non-sortable

Author: ygongdev

README.md

@@ -212,6 +212,13 @@ export default Ember.Route.extend({
   {{/sortable-item}}
 ```
 
+### Disabling Drag (Experimental)
+`sortable-item` exposes an optional `isDraggingDisabled` flag that you can use to disable `drag` on the particular item.
+This flag is intended as an utility to make your life easier with 3 main benefits:
+1. You can now specify which `sortable-item` are not intended to be draggable/sortable.
+2. You do not have to duplicate the `sortable-item` UI just for the purpose of disabling the `sorting` behavior.
+3. Allows you to access the entire list of `models` for your `onChange` action, which can now be a mix of sortable and non-sortable items.
+
 ### Data down, actions up
 
 No data is mutated by `sortable-group` or `sortable-item`. In the spirit of “data down, actions up”, a fresh array containing the models from each item in their new order is sent via the group’s `onChange` action.

addon/components/sortable-group.js

@@ -705,7 +705,7 @@ export default Component.extend({
     },
 
     deregisterItem(item) {
-      this._registerItem(item);
+      this._deregisterItem(item);
     },
 
     setSelectedItem(item) {

addon/components/sortable-item.js

@@ -133,6 +133,14 @@ export default Component.extend({
   */
   spacing: 0,
 
+  /**
+    Removes the ability for the current item to be dragged
+    @property isDraggingDisabled
+    @type Boolean
+    @default false
+  */
+  isDraggingDisabled: false,
+
   /**
     @private
     Allows host instance to use the `group` property for something else with
@@ -251,6 +259,11 @@ export default Component.extend({
    * @private
    */
   _primeDrag(startEvent) {
+    // Prevent dragging if the sortable-item is disabled.
+    if (this.get('isDraggingDisabled')) {
+      return;
+    }
+
     let handle = this.get('handle');
 
     if (handle && !startEvent.target.closest(handle)) {