bug#23076: 24.5; vc-git: add a new variable for log output coding system

[Eli Zaretskii <eliz@gnu.org>]

> From: Nikolay Kudryavtsev <nikolay.kudryavtsev@gmail.com>
> Date: Mon, 21 Mar 2016 22:01:59 +0300
> 
> 1. (setq vc-git-commits-coding-system 'windows-1251)
> 2. Clone https://github.com/sg2002/vc-git-bugs
> 3. Run vc-log on it. This would give you broken output.
> 4. Evaluate the whole fix.el file from the repo.
> 5. Run vc-log again. Now you would get the proper "Русскоязычный 
> коммит." in it.

(By "vc-log", I presume you meant "C-x v l".  There's no vc-log
command, AFAICT.)

Please try the latest emacs-25 branch in the Emacs repository and tell
which problems for this bug remain.

I actually don't understand the reasons for the 1st step above: the
log message is reported by Git in UTF-8, so if I avoid the first step,
then step 3 produces the correct output.

> Adding a new variable is the only way to setup git with Russian commit 
> logs on Windows, while fulfilling all three of the following requirements:
> 1. Committing from Emacs in Russian should work.
> 2. vc-log should work in Emacs.
> 3. git log should work outside of Emacs.

So if any problems remain, they are either in

  1. Committing from Emacs in Russian should work.

or in

  3. git log should work outside of Emacs.

Please tell which one(s) of these don't work, and why.  I tried "git
log" outside of Emacs, and it produced UTF-8 output.  If it doesn't do
that for you, perhaps you've customized Git itself?  If so, what
happens if you remove that customization?

As for committing from Emacs in Russian, that should again work if you
use UTF-8, so I'm unsure what problems prevent you from having that.

Thanks.