help: internals topic for wire protocol The Mercurial wire protocol is under-documented. This includes a lack of source docstrings and comments as well as pages on the official wiki. This patch adds the beginnings of "internals" documentation on the wire protocol. The documentation should have nearly complete coverage on the lower-level parts of the protocol, such as the different transport mechanims, how commands and arguments are sent, capabilities, and, of course, the commands themselves. As part of writing this documentation, I discovered a number of deficiencies in the protocol and bugs in the implementation. I've started sending patches for some of the issues. I hope to send a lot more. This patch starts with the scaffolding for a new internals page.