Re: insert-file-contents and format-decode

[Richard Stallman <rms@gnu.org>]

    !   (let (value size old-undo)
    !     ;; Record only one undo entry for the insertion.  Inhibit point-motion and
    !     ;; modification hooks as with `insert-file-contents'.
    !     (let ((inhibit-point-motion-hooks t)
    ! 	  (inhibit-modification-hooks t))
    !       ;; Don't bind `buffer-undo-list' to t here to assert that
    !       ;; `insert-file-contents' may record whether the buffer was unmodified
    !       ;; before.
    !       (let ((format-alist nil))
    ! 	(setq value (insert-file-contents filename nil beg end))
    ! 	(setq size (nth 1 value)))
    !       (when (consp buffer-undo-list)
    ! 	(let ((head (car buffer-undo-list)))
    ! 	  (when (and (consp head)
    ! 		     (equal (car head) (point))
    ! 		     (equal (cdr head) (+ (point) size)))
    ! 	    ;; Remove first entry from `buffer-undo-list', we shall insert
    ! 	    ;; another one below.
    ! 	    (setq old-undo (cdr buffer-undo-list)))))

That pateh is basically good, but it could be simpler.  Instead of
letting insert-file-contents produce an undo entry and taking it off
and taking it apart, it would be better to inhibit undo around
insert-file-contents and generate the undo entry from scratch in all
cases.  When no format decoding is done, VALUE has the size you need.