Add --action_graph:include_cmdline to the documentation for the dump command.

RELNOTES: None.
PiperOrigin-RevId: 213283653
diff --git a/site/docs/user-manual.html b/site/docs/user-manual.html
index b6e66e5..f7dcecc 100644
--- a/site/docs/user-manual.html
+++ b/site/docs/user-manual.html
@@ -3430,6 +3430,8 @@
   <li><code class='flag'>--action_graph:targets=target1,target2,...</code>
     filters the actions to the comma-separated list of targets when dumping the
     action graph.</li>
+  <li><code class='flag'>--action_graph:include_cmdline</code> Include the command lines of actions
+    in the action graph dump.</li>
 </ul>
 
   <h4 id='memory-tracking'>Memory tracking</h4>