VC to bind coding-system while invoking Git

[Eli Zaretskii]

vc-git-command should bind coding-system-for-read/write to the value
of vc-git-commits-coding-system (utf-8 by default).  Currently, we
only do that for a handful of Git commands, which is inconsistent.
The result is, for example, that typing RET in a *vc-change-log*
buffer might show the non-ASCII characters incorrectly if the default
for process-coding-system is not UTF-8.

Likewise with vc-git--call.

Any objections?