VC hg backend that use mercurial command server.

[Andrii Kolomoiets <andreyk.mad@gmail.com>]

Hello.

I'm finally ready to present you VC hg backend that uses mercurial
command server. It allows to communicate with single mercurial process
over pipe rather than execute hg process for every command.

Also there is a possibility to answer to hg questions interactively.
It's useful during merge when hg is in doubt about right action.

Besides that it has some changes and improvements described in
commentary section of the package.

Hg process can be controlled via pipe (Linux, MacOS) or pty (TRAMP,
Windows).

I think this package can make working with hg repositories more
pleasant :)

I want to contribute to improve built-in hg support.

May I ask which way it can be done better?

I see that all other backends are process based, so can this
single-process backend be acceptable? If so then is it better to replace
hg backend (saving customizable options as much as possible) or provide
two backends which share same options?

Source code is here:
https://github.com/muffinmad/emacs-vc-hgcmd/blob/master/vc-hgcmd.el

Hope you'll find it useful ;)


Andrii