diff -r b9faf94ee196 -r 2852933fc942 mercurial/commands.py
--- a/mercurial/commands.py	Wed Jun 22 01:55:00 2011 +0200
+++ b/mercurial/commands.py	Fri Jun 24 10:51:05 2011 +0200
@@ -5051,6 +5051,9 @@
     found, the working directory is updated to the specified
     changeset.
 
+    Update sets the working directory's parent revison to the specified
+    changeset (see :hg:`help parents`).
+
     The following rules apply when the working directory contains
     uncommitted changes: