Add documentation header

www/manager5/data/DiffStore.js

+/*
+ * The DiffStore acts as proxy between an UpdateStore instance and a component.
+ * Its purpose is to redisplay the component *only* if the data has been changed
+ * inside the UpdateStore, to avoid the annoying visual flickering of using
+ * the UpdateStore directly.
+ *
+ * Implementation:
+ * The DiffStore monitors via mon() the 'load' events sent by the target store.
+ * On each 'load' event, the DiffStore compares its own content with the target
+ * store (call to cond_add_item()) and then fires a 'refresh' event.
+ * The 'refresh' event will automatically trigger a view refresh on the component
+ * who binds to this store.
+ */
+
 /* Config properties:
- * rstore: A storage to track changes
+ * rstore: A target store to track changes
  * Only works if rstore has a model and use 'idProperty'
  */
 Ext.define('PVE.data.DiffStore', {