On Wed, 30 Sep 2015 03:30:12 +0900, Stephen J. Turnbull wrote:
  > What is the proper way to use vc.git.el on 21.4?
 
 If vc-git requires UTF-8, as your question appears to imply, then
 there is no "proper" way to use it in XEmacs 21.4. 
Well, unlike vc.el which tries to accomodate (see 
vc-coding-system-for-diff), vc-git.el assumes "All the world's utf-8 - 
and if it isn't, that is Somebody Else's Problem(tm)'. From cursory 
googling, the utf-8 is not a git requirement.
I ended up with the following patch (comments?) which works for me:
--- lisp/vc/vc-git.el.orig      2007-08-23 21:27:53.000000000 +0000
+++ lisp/vc/vc-git.el
@@ -35,7 +35,19 @@
 
 (eval-when-compile (require 'cl))
 
-(defvar git-commits-coding-system 'utf-8
+(defun vc-git-determine-coding-system ()
+
+  "Return utf-8 om 21.5, or the current buffer's coding on 21,4"
+
+  (if (and (featurep 'xemacs)
+          (<= emacs-major-version 21)
+          (<  emacs-minor-version 5))
+      (if (boundp 'buffer-file-coding-system)
+         buffer-file-coding-system
+       'undecided)
+    'utf-8))
+
+(defvar git-commits-coding-system (vc-git-determine-coding-system)
   "Default coding system for git commits.")
 
 (defun vc-git--run-command-string (file &rest args)
-- from reading vc-git.el, I am not sure how exactly the encoding is 
used - by XEmacs? By git? - and whether - where? - an actual conversion 
takes place. But, as I said, this works with 21.4.23 and 21.5.27 here.
Cheerio,
hauke
-- 
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