bug#58479: 29.0.50; [feature/noverlay] Displaced overlays in notmuch search buffers after refreshing

[Stefan Monnier]

> New repro, see function below.  Symptoms: despite inserting two lines of
> text, and there being a single overlay at (1,1) with the 'invisible
> prop, all I see in the buffer is the ellipsis.  I can cursor around and
> see the position change in the mode line, but the display never changes.
> With the cursor at EOB it appears after the ellipsis.  Anywhere else and
> the cursor appears before it.
>
> (defun my-b58479-4 ()
>   (interactive)
>   (with-current-buffer (get-buffer-create "*b58479*")
>     (kill-all-local-variables)
>     (delete-all-overlays)
>     (setq buffer-read-only nil)
>     (setq buffer-file-name nil)
>     (setq buffer-undo-list nil)
>     (let ((inhibit-read-only t)
>           (inhibit-modification-hooks t))
>       (erase-buffer))
>     (add-to-invisibility-spec (cons 'ellipsis t))
>     (goto-char (point-max))
>     (insert "first line\nsecond line\n")
>     (let ((overlay (make-overlay 1 1)))
>       (overlay-put overlay 'invisible 'ellipsis))
>     (display-buffer (current-buffer))))

Hmm... I can't see the problem on my end.
I did

    % src/emacs -Q
    <mouse-2> to paste the above code into *scratch*
    C-M-x
    M-x my-b58479-4 RET

but this shows me a buffer with 2 lines and no ellipsis.
[ With the latest code from `feature/noverlay` whch I just pushed with
  your (rebased) changes.  ]


        Stefan


PS: You can use `with-silent-modifications` around the `erase-buffer`
and `insert` calls: it will do the dance with the other variables for you.