bug#71424: 29.3; auto-revert-use-notify buggy interaction with indirect buffers

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sat, 08 Jun 2024 11:30:08 -0400
> From: "Aaron Zeng" <z@bcc32.com>
> Cc: 71424@debbugs.gnu.org
> 
> On Sat, Jun 8, 2024, at 03:03, Eli Zaretskii wrote:
> 
> > To see that at least the basic functionality works in Emacs, I did the
> > following:
> >
> >   emacs -Q
> >   C-x C-f SOME-FILE RET
> >   M-x global-auto-revert-mode RET
> >   M-x clone-indirect-buffer RET
> >
> > Then, outside Emacs, typed from the shell prompt
> >
> >   $ cat OTHER-FILE >> SOME-FILE
> >
> > where OTHER-FILE is some other existing file.  After that, I saw both
> > the base buffer's text and that of its indirect clone change to
> > reflect the appended text.
> 
> Indeed, while the indirect buffer is live, everything works fine.  However, after you kill the indirect buffer, then the buffer no longer gets auto-reverted when you modify SOME-FILE outside Emacs.

Right.  Michael, is the below the correct fix?

diff --git a/lisp/autorevert.el b/lisp/autorevert.el
index a23d536..ab69add 100644
--- a/lisp/autorevert.el
+++ b/lisp/autorevert.el
@@ -378,8 +378,11 @@ auto-revert-debug
 (defun auto-revert-remove-current-buffer (&optional buffer)
   "Remove BUFFER from `auto-revert-buffer-list'.
 BUFFER defaults to `current-buffer'."
-  (setq auto-revert-buffer-list
-        (delq (or buffer (current-buffer)) auto-revert-buffer-list)))
+  (let ((buf (or buffer (current-buffer))))
+    ;; Don't remove the watch if we are killing an indirect buffer.
+    (or (buffer-base-buffer buf)
+        (setq auto-revert-buffer-list
+              (delq buf auto-revert-buffer-list)))))
 
 ;;;###autoload
 (define-minor-mode auto-revert-mode
@@ -639,7 +642,9 @@ auto-revert-set-timer
 
 (defun auto-revert-notify-rm-watch ()
   "Disable file notification for current buffer's associated file."
-  (when-let ((desc auto-revert-notify-watch-descriptor))
+  (when-let ((desc
+              (and (buffer-base-buffer)
+                   auto-revert-notify-watch-descriptor)))
     (setq auto-revert--buffer-by-watch-descriptor
           (assoc-delete-all desc auto-revert--buffer-by-watch-descriptor))
     (ignore-errors