merge: release notes DOCS-290

Author: Sam Kleinman

source/release-notes/2.2.txt

@@ -145,6 +145,29 @@ Tag Aware Sharding
 
 .. including tagging
 
+Compatibility Changes
+~~~~~~~~~~~~~~~~~~~~~
+
+.. TODO add sections here to describe compatibility changes with
+   regards to authentication, drivers, and mongos'
+
+``findAndMondify`` Returns Null value for Upserts
+`````````````````````````````````````````````````
+
+In version 2.2, for :term:`upsert` operations, :dbcommand:`findAndModify`
+commands will now return the following output:
+
+.. code-block:: javascript
+
+   {'ok': 1.0, 'value': null}
+
+In the :program:`mongo` shell, :dbcommand:`findAndModify` operations
+running as upserts will only output a ``null`` value.
+
+Previously, in version 2.0 these operations would return an empty
+document, e.g. ``{ }``.
+
+See: :issue:`SERVER-6226`.
 
 Naming
 ~~~~~~