bug#35418: [PATCH] Don't poll auto-revert files that use notification

["Mattias Engdegård" <mattiase@acm.org>]

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8 maj 2019 kl. 15.28 skrev Eli Zaretskii <eliz@gnu.org>:
>> 
>>> OK, so how about adding such a variable as part of this improvement?
>> 
>> If it's all the same to you, I'd like to keep it separate.
> 
> I don't understand why: the change as it is looks a bit unclean to me,
> whereas the effort to make it cleaner and more future-proof is not a
> substantial one.

How about dropping the Dired special case for the time being? Then the immediate bug is fixed, and all we need to worry about is the 2.5 second delay to Dired auto-revert updates, which we can fix separately in a manner of our choosing.

Simplified patch attached.

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From 0ac97e913ffb3096934c64715f12921af5fce64a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mattias=20Engdeg=C3=A5rd?= <mattiase@acm.org>
Date: Wed, 8 May 2019 00:02:59 +0200
Subject: [PATCH] Don't use file notification on non-file buffers

Most non-file buffers aren't served by file notification in
auto-revert mode; typically, they need to be polled, like the Buffer List.
With `auto-revert-avoid-polling', setting a useless notification means
that such buffers may never be updated at all (bug#35418).

* lisp/autorevert.el (auto-revert-buffers):
Modify condition for using notification.
---
 lisp/autorevert.el | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lisp/autorevert.el b/lisp/autorevert.el
index 7cd5e7ee8b..fbaffbf0d6 100644
--- a/lisp/autorevert.el
+++ b/lisp/autorevert.el
@@ -859,7 +859,8 @@ the timer when no buffers need to be checked."
               (when (auto-revert-active-p)
                 ;; Enable file notification.
                 (when (and auto-revert-use-notify
-                           (not auto-revert-notify-watch-descriptor))
+                           (not auto-revert-notify-watch-descriptor)
+                           buffer-file-name)
                   (auto-revert-notify-add-watch))
                 (auto-revert-handler)))))
 	(setq bufs (cdr bufs)))
-- 
2.20.1 (Apple Git-117)