keepalive: implement readinto() This is part of the standard I/O interface. It is used by the framing protocol. So we need to implement it so frames can be decoded. Differential Revision: https://phab.mercurial-scm.org/D2984

wireproto: port protocol handler to zope.interface zope.interface is superior to the abc module. Let's port to it. As part of this, we add tests for interface conformance for classes implementing the interface. Differential Revision: https://phab.mercurial-scm.org/D2983

wireproto: separate commands tables for version 1 and 2 commands We can't easily reuse existing command handlers for version 2 commands because the response types will be different. e.g. many commands return nodes encoded as hex. Our new wire protocol is binary safe, so we'll wish to encode nodes as binary. We /could/ teach each command handler to look at the protocol handler and change behavior based on the version in use. However, this would make logic a bit unwieldy over time and would make it harder to design a unified protocol handler interface. I think it's better to create a clean break between version 1 and version 2 of commands on the server. What I imagine happening is we will have separate @wireprotocommand functions for each protocol generation. Those functions will parse the request, dispatch to a common function to process it, then generate the response in its own, transport-specific manner. This commit establishes a separate table for tracking version 1 commands from version 2 commands. The HTTP server pieces have been updated to use this new table. Most commands are marked as both version 1 and version 2, so there is little practical impact to this change. A side-effect of this change is we now rely on transport registration in wireprototypes.TRANSPORTS and certain properties of the protocol interface. So a test had to be updated to conform. Differential Revision: https://phab.mercurial-scm.org/D2982

wireproto: mark SSHv2 as a version 1 transport The version component is used for filtering/routing wire protocol commands to their proper handler. The actual version 2 of the wire protocol commands will use a different encoding of responses. We already have tests using the version 2 SSH transport and version 2 of the wire protocol commands won't be implemented atomically. This commit marks the SSHv2 transport as version 1 so it will still invoke the version 1 commands. Once the commands are all implemented in version 2, we can restore its proper behavior. Some tests had to be disabled as a result of this change. Differential Revision: https://phab.mercurial-scm.org/D2981