largefiles: register wire protocol commands with modern APIs The wireproto.wireprotocommand decorator is the preferred mechanism for registering wire protocol commands. In addition, wireproto.commands is no longer a 2-tuple and use of that 2-tuple API should be considered deprecated. This commit ports largefiles to use wireproto.wireprotocommand() and ports to the "commandentry" API. As part of this, the definition of the "lheads" wire protocol command is moved to the proper stanza. We stop short of actually using wireprotocommand as a decorator in order to minimize churn. We should ideally move wire protocol commands to the registrar mechanism. But that's for another changeset. Differential Revision: https://phab.mercurial-scm.org/D2018

wireproto: function for testing if wire protocol command is available Currently, we perform simple membership testing for whether a wire command is available. In the future, not all wire protocol commands will be available on all transports. For example, a legacy transport may not support newer commands. In preparation of this, teach the protocol handlers to call into a function to determine if a wire protocol command is available. That function currently does membership testing like before, so behavior should be identical. In the case of the HTTP server, behavior is a bit wonkier. "cmd" is used by both the wire protocol and hgweb. We do want the protocol handler to handle requests for all commands that look like wire protocol commands, even if they aren't available. Otherwise, the fallback to hgweb would only confuse automated clients and make it easier for hgweb to accidentally implement a "cmd" that is identical to wire protocol commands (since they aren't centrally registered). Differential Revision: https://phab.mercurial-scm.org/D1999

wireproto: define and use types for wire protocol commands Wire protocol commands have historically been declared as 2-tuples in wireproto.commands. There are some additional features I'd like to implement that require going beyond 2-tuples. But because the 2-tuple API (both destructuring assignment and direct assignment into the dict) is used throughout the code base and in 3rd party extensions, we can't do a trivial type change. This commit creates a new "commandentry" type to represent declared wire protocol commands. It implements __getitem__ and __iter__ so it can quack like a 2-tuple. The @wireprotocommand decorator now creates "commandentry" instances. We also create a "commanddict" type to represent the dictionary of declared wire protocol commands. It inherits from "dict" but provides a custom __setitem__ to coerce passed 2-tuples to "commandentry" instances. wireproto.commands is now an instance of this type. Various callers in core rely on the new functionality. And tests pass. So I'm reasonably confident things will "just work" in 3rd party extensions as well. Differential Revision: https://phab.mercurial-scm.org/D1998

wireproto: improve docstring for @wireprotocommand I'm about to add more arguments and want them to be documented. Plus, good documentation is nice to have. Differential Revision: https://phab.mercurial-scm.org/D1997

wireproto: remove unnecessary exception trapping The `try..except error.Abort` was added in 8474be4412ca back in 2012. The intent was to ensure a failing pushkey hook didn't crash the server. Since that changeset, repo.pushkey() and the hooks mechanism is now much more robust about trapping errors itself. As such, we no longer need this try..except block. So it has been removed. Differential Revision: https://phab.mercurial-scm.org/D1996

sshpeer: implement peer for version 2 of wire protocol Since the protocol is now negotiated before we construct a peer instance, we can return the negotiated protocol from the handshake function and instantiate an appropriate peer class for the protocol. Version 2 of the SSH protocol is currently identical to version 1 post handshake. So our sshv2peer class just inherits from sshv1peer for the time being. This will obviously change over time. Differential Revision: https://phab.mercurial-scm.org/D2063

sshpeer: rename sshpeer class to sshv1peer (API) With the introduction of version 2 of the SSH wire protocol, we will need a new peer class to speak that protocol because it will be too difficult to shoehorn a single class to speak two protocols. We rename sshpeer.sshpeer to sshpeer.sshv1peer to reflect the fact that there will be multiple versions of the peer depending on the negotiated protocol. .. api:: sshpeer.sshpeer renamed to sshpeer.sshv1peer. Differential Revision: https://phab.mercurial-scm.org/D2062