update: allow -c to jump branches if clean

mercurial/commands.py

@@ -3045,7 +3045,7 b' def update(ui, repo, node=None, rev=None'
             raise util.Abort(_("you can't specify a revision and a date"))
         rev = cmdutil.finddate(ui, repo, date)
 
-    if clean:
+    if clean or check:
         return hg.clean(repo, rev)
     else:
         return hg.update(repo, rev)