push: restore contents of HG_URL for hooks (issue4268)

mercurial/exchange.py

@@ -286,7 +286,7 b' def _pushchangeset(pushop):'
         # ssh: return remote's addchangegroup()
         # http: return remote's addchangegroup() or 0 for error
         pushop.ret = pushop.remote.unbundle(cg, remoteheads,
-                                            'push')
+                                            pushop.repo.url())
     else:
         # we return an integer indicating remote head count
         # change