--- a/mercurial/commands.py	Tue Jul 20 20:52:23 2010 +0200
+++ b/mercurial/commands.py	Tue Jul 20 15:07:10 2010 -0500
@@ -3157,7 +3157,7 @@
                     ui.note(_('saving current version of %s as %s\n') %
                             (rel, bakname))
                     if not opts.get('dry_run'):
-                        util.copyfile(target, bakname)
+                        util.rename(target, bakname)
                 if ui.verbose or not exact:
                     msg = xlist[1]
                     if not isinstance(msg, basestring):