diff -r 4a069064a39b -r 25af3f17ce95 mercurial/commands.py
--- a/mercurial/commands.py	Tue May 09 11:12:45 2006 -0700
+++ b/mercurial/commands.py	Tue May 09 13:29:55 2006 -0700
@@ -2712,6 +2712,7 @@
     release. Please use the rollback command instead.  For usage
     instructions, see the rollback command.
     """
+    ui.warn(_('(the undo command is deprecated; use rollback instead)\n'))
     repo.undo()
 
 def update(ui, repo, node=None, merge=False, clean=False, force=None,