wireproto: do not hash when heads == ['force']

Changeset 88f0e41d8802 introduced the unbundlehash capability and
unconditionally hashed the heads on the client side. By mistake, the
heads were also cased in the heads == ['force'] case.

mercurial/wireproto.py

@@ -139,7 +139,7 b' class wirerepository(repo.repository):'
         remote server as a bundle. Return an integer indicating the
         result of the push (see localrepository.addchangegroup()).'''
 
-        if self.capable('unbundlehash'):
+        if heads != ['force'] and self.capable('unbundlehash'):
             heads = encodelist(['hashed',
                                 util.sha1(''.join(sorted(heads))).digest()])
         else: