thru file-name-sans-versions, because it never has version numbers.
;; `make-backup-file-name' will get us the right directory for
;; ordinary or numeric backups. It might create a directory for
;; backups as a side-effect, according to `backup-directory-alist'.
- (let* ((filename (file-name-sans-versions
- (make-backup-file-name filename)))
+ (let* ((filename (make-backup-file-name filename))
(file (file-name-nondirectory filename))
(dir (file-name-directory filename))
(comp (file-name-all-completions file dir))