Re: Redifine make-backup-file-name has no effect

[Gerd Moellmann]

"Jan D." <Jan.Djarv@mbox200.swipnet.se> writes:

> In article <3BD964D4.C26E06E9@lu.erisoft.se>,
> Jan Djärv <Jan.Djarv@epl.ericsson.se> wrote:
> 
> (about cutomizing make-backup-file-name-function does not call that
> function, or at least still uses file~ as backup file name)
> 
> The error is in files.el, function find-backup-file-name.  It uses
> the result from make-backup-file-name-1 directly, thus bypassing
> the cutomization hook.
> 
> Here's a patch:
> 
> Index: lisp/files.el
> --- lisp/files.el.orig        Sun Oct 28 15:13:39 2001
> +++ lisp/files.el     Sun Oct 28 15:11:38 2001
> @@ -2422,7 +2422,7 @@
>                                       -1))
>           (file-error (setq possibilities nil)))
>         (if (not deserve-versions-p)
> -           (list (concat basic-name "~"))
> +           (list (make-backup-file-name fn))
>           (cons (format "%s.~%d~" basic-name (1+ high-water-mark))
>                 (if (and (> number-to-delete 0)
>                          ;; Delete nothing if there is overflow
> 
> 

Thanks, Jan.  Alas, I'm not sure what the right fix is here because
I'm not sure from the docs if a make-backup-file-name-function is
supposed to return a file name including versions or not.  There are
indirect hints that it might have to return file names with versions,
like the code of file-newest-backup using file-name-sans-versions,
but not enough to be sure.

If it's supposed to do that, I think the fix would be

*** files.el    2001/10/29 14:13:31     1.532
--- files.el    2001/10/29 14:13:50
***************
*** 2411,2416 ****
--- 2411,2417 ----
      (if handler
        (funcall handler 'find-backup-file-name fn)
        (if (or (eq version-control 'never)
+             (not (null make-backup-file-name-function))
              ;; We don't support numbered backups on plain MS-DOS
              ;; when long file names are unavailable.
              (and (eq system-type 'ms-dos)

Richard, could you please comment?