diff -r aafe12bd7174 -r f29b674cc221 mercurial/commands.py
--- a/mercurial/commands.py	Mon Sep 15 23:39:11 2008 +0100
+++ b/mercurial/commands.py	Wed Sep 17 11:34:37 2008 +0200
@@ -2814,7 +2814,8 @@
     """update working directory
 
     Update the repository's working directory to the specified revision,
-    or the tip of the current branch if none is specified.
+    or the tip of the current branch if none is specified. Use null as
+    the revision to remove the working copy (like 'hg clone -U').
 
     If the requested revision is a descendant of the working
     directory, any outstanding changes in the working directory will