bug#23075: 24.5; vc-git-command should use coding-system-for-read

[Nikolay Kudryavtsev]

> Then the encoding of the file being visited is no longer as relevant as in the 
> use case you describe.
That's true, and whoever wrote this part of vc was aware of the issue, 
as you can see from that comment. The simple fix at least allow getting 
diff for the file in a different encoding, even if you have to diff that 
file alone.

I can confirm that Oscar's issue with HELLO is the same thing. What he 
described as garbage was probably the result of vc-diff encoded in utf-8 
since that's the default value of vc-git-commits-coding-system.

--
Best Regards,
Nikolay Kudryavtsev