bug#12855: 24.2; The Messages buffer stops following the appended lines.

[Stefan Monnier]

> Since this bug constitutes a considerable annoyance and a regression wrt
> 23.4 I'd like to install the attached patch on the Emacs 24 branch.  It
> principally only adds the necessary TYPE argument to the `copy-marker'
> calls but looks more complex because I have to do this in the right
> buffer and therefore rearranged the code a bit.  OK to install?

Yes.

> -     (let ((start (window-start window))
> -           (point (window-point window)))
> -       (setq entry
> -             (cons buffer
> -                   (if entry
> -                       ;; We have an entry, update marker positions.
> -                       (list (set-marker (nth 1 entry) start)
> -                             (set-marker (nth 2 entry) point))
> -                     ;; Make new markers.
> -                     (list (copy-marker start)
> -                           (copy-marker point)))))
> -
> +     (let* ((start
> +             (if entry
> +                 (set-marker (nth 1 entry) (window-start window))
> +               (copy-marker (window-start window))))
> +            (point
> +             (if entry
> +                 (set-marker (nth 2 entry) (window-point window))
> +               (copy-marker
> +                ;; Preserve window-point-insertion-type (Bug#12855).
> +                (window-point) window-point-insertion-type))))
>         (set-window-prev-buffers
> -        window (cons entry (window-prev-buffers window))))))))
> +        window
> +        (cons (list buffer start point)
> +              (window-prev-buffers window))))))))

I don't understand why you massaged the code this way instead of just
adding window-point-insertion-type to the last copy-marker call, but
I presume there's a good reason.


        Stefan