revert: use term "uncommitted merge" in help text stable

revert: use term "uncommitted merge" in help text

to make sure users can't possibly be mislead to try this for canceling a
*merge changeset*.

--- a/mercurial/commands.py	Tue Jul 10 21:26:18 2012 +0200
+++ b/mercurial/commands.py	Mon Jul 09 17:51:46 2012 +0200
@@ -4822,8 +4822,10 @@
     """restore files to their checkout state
 
     .. note::
+
        To check out earlier revisions, you should use :hg:`update REV`.
-       To cancel a merge (and lose your changes), use :hg:`update --clean .`.
+       To cancel an uncommitted merge (and lose your changes), use
+       :hg:`update --clean .`.
 
     With no revision specified, revert the specified files or directories
     to the contents they had in the parent of the working directory.