diff -r aebc3f64b20f -r ea2a9c13afc6 mercurial/commands.py
--- a/mercurial/commands.py	Mon Aug 28 21:49:02 2006 +0200
+++ b/mercurial/commands.py	Tue Aug 29 19:02:57 2006 +0200
@@ -2291,7 +2291,8 @@
     """
 
     if not pats and not opts['all']:
-        raise util.Abort(_('no files or directories specified'))
+        raise util.Abort(_('no files or directories specified; '
+                           'use --all to revert the whole repo'))
 
     parent, p2 = repo.dirstate.parents()
     if opts['rev']: