add an example of what to expect from docker diff, and what the 3 codes mean

docs/sources/commandline/cli.rst

@@ -231,9 +231,33 @@ Full -run example
 
 ::
 
-    Usage: docker diff CONTAINER [OPTIONS]
+    Usage: docker diff CONTAINER
+ 
+    List the changed files and directories in a container's filesystem
 
-    Inspect changes on a container's filesystem
+There are 3 events that are listed in the 'diff':
+
+1. ```A``` - Add
+2. ```D``` - Delete
+3. ```C``` - Change
+
+for example:
+
+.. code-block:: bash
+
+	$ sudo docker diff 7bb0e258aefe
+
+	C /dev
+	A /dev/kmsg
+	C /etc
+	A /etc/mtab
+	A /go
+	A /go/src
+	A /go/src/github.com
+	A /go/src/github.com/dotcloud
+	A /go/src/github.com/dotcloud/docker
+	A /go/src/github.com/dotcloud/docker/.git
+	....
 
 .. _cli_events: