wireproto: use maybecapturestdio() for push responses (API) The "pushres" and "pusherr" response types currently call proto.restore() in the HTTP protocol. This completes the pairing with proto.redirect() that occurs in the @wireprotocommand functions. (But since the SSH protocol has a no-op redirect(), it doesn't bother calling restore() because it would also be a no-op.) Having the disconnect between these paired calls is very confusing. Knowing that you must use proto.redirect() if returning a "pushres" or a "pusherr" is even wonkier. We replace this confusing code with our new context manager for [maybe] capturing output. The "pushres" and "pusherr" types have gained an "output" argument to their constructor and an attribute to hold captured data. The HTTP protocol now retrieves output from these objects. .. api:: ``wireproto.pushres`` and ``wireproto.pusherr`` now explicitly track stdio output. Differential Revision: https://phab.mercurial-scm.org/D2082