DOCS-1077 add missing multi parameter to update examples

source/reference/operator/inc.txt

@@ -6,30 +6,31 @@ $inc
 
 .. operator:: $inc
 
-   The :operator:`$inc` operator increments a value by a specified
-   amount if field is present in the document. If the field does not
-   exist, :operator:`$inc` sets field to the number value. For
-   example:
+   The :operator:`$inc` operator increments a value of a field by a
+   specified amount. If the field does not exist, :operator:`$inc` sets
+   the field to the specified amount. :operator:`$inc` accepts positive
+   and negative incremental amounts.
+
+   The following example increments the value of ``field1`` by the
+   value of ``amount`` for the *first* matching document in the
+   collection where ``field`` equals ``value``:
 
    .. code-block:: javascript
 
-      db.collection.update( { field: value }, { $inc: { field1: amount } } );
+      db.collection.update( { field: value }, 
+                            { $inc: { field1: amount } } );
 
-   In this example, for documents in ``collection`` where
-   ``field`` has the value ``value``, the value of ``field1``
-   increments by the value of ``amount``. The above operation only
-   increments the *first* matching document *unless* you specify
-   multi-update:
+   To update all matching documents in the collection, specify
+   ``multi:true`` in the :method:`~db.collection.update()` method:
 
    .. code-block:: javascript
 
-      db.collection.update( { age: 20 }, { $inc: { age: 1 } } );
-      db.collection.update( { name: "John" }, { $inc: { age: 1 } } );
-
-   In the first example all documents that have an ``age`` field with
-   the value of ``20``, the operation increases ``age`` field by
-   one. In the second example, in all documents where the ``name``
-   field has a value of ``John`` the operation increases the value
-   of the ``age`` field by one.
+      db.collection.update( { age: 20 }, { $inc: { age: 1 } }, { multi: true } );
+      db.collection.update( { name: "John" }, { $inc: { age: 2 } }, { multi: true } );
 
-   :operator:`$inc` accepts positive and negative incremental amounts.
+   The first :method:`~db.collection.update()` operation increments the
+   value of the ``age`` field by ``1`` for all documents in the
+   collection that have an ``age`` field equal to ``20``. The
+   second operation increments the value of the ``age`` field by ``2``
+   for all documents in the collection with the ``name`` field
+   equal to ``"John"``.