wireproto: in batch queries, support queries with immediate responses


wireproto: in batch queries, support queries with immediate responses

listkeys and pushkey return without querying the remote when the
remote doesn't support such queries. Before this change, the batching
code didn't handle this convention, resulting in this kind of error:

$ hg pull ssh://user@dummy/repo1 -r tip -B a
pulling from ssh://user@dummy/repo1
remote: ** Unknown exception encountered with possibly-broken third-party extension disable-lookup
remote: ** which supports versions unknown of Mercurial.
remote: ** Please disable disable-lookup and try your action again.
remote: ** If that fixes the bug please report it to the extension author.
remote: ** Python 2.7.15+ (default, Oct  2 2018, 22:12:08) [GCC 8.2.0]
remote: ** Mercurial Distributed SCM (version 4.8.1+586-ef54bd33b476+20181224)
remote: ** Extensions loaded: disable-lookup
remote: Traceback (most recent call last):
remote:   File "/tmp/hgtests.i66Npc/install/bin/hg", line 43, in <module>
remote:     dispatch.run()
remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/dispatch.py", line 99, in run
remote:     status = dispatch(req)
remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/dispatch.py", line 225, in dispatch
remote:     ret = _runcatch(req) or 0
remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/dispatch.py", line 376, in _runcatch
remote:     return _callcatch(ui, _runcatchfunc)
remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/dispatch.py", line 384, in _callcatch
remote:     return scmutil.callcatch(ui, func)
remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/scmutil.py", line 166, in callcatch
remote:     return func()
remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/dispatch.py", line 367, in _runcatchfunc
remote:     return _dispatch(req)
remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/dispatch.py", line 1021, in _dispatch
remote:     cmdpats, cmdoptions)
remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/dispatch.py", line 756, in runcommand
remote:     ret = _runcommand(ui, options, cmd, d)
remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/dispatch.py", line 1030, in _runcommand
remote:     return cmdfunc()
remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/dispatch.py", line 1018, in <lambda>
remote:     d = lambda: util.checksignature(func)(ui, *args, **strcmdopt)
remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/util.py", line 1670, in check
remote:     return func(*args, **kwargs)
remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/commands.py", line 5257, in serve
remote:     s.serve_forever()
remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/wireprotoserver.py", line 797, in serve_forever
remote:     self.serveuntil(threading.Event())
remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/wireprotoserver.py", line 804, in serveuntil
remote:     _runsshserver(self._ui, self._repo, self._fin, self._fout, ev)
remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/wireprotoserver.py", line 656, in _runsshserver
remote:     rsp = wireprotov1server.dispatch(repo, proto, request)
remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/wireprotov1server.py", line 74, in dispatch
remote:     return func(repo, proto, *args)
remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/wireprotov1server.py", line 195, in batch
remote:     data[k] = vals[k]
remote: KeyError: 'namespace'
abort: unexpected response: empty string

Differential Revision: https://phab.mercurial-scm.org/D5482