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

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

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Actually, the comment added in the last patch was inaccurate and referred to a previous attempt.
Revised patch attached (the actual condition is unchanged).

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From 52935159130964f7a4979840985c923a8d84a9ac 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).

An exception is made for Dired, as that mode works well with
notification on the directory.

* lisp/autorevert.el (auto-revert-buffers):
Modify condition for using notification.
---
 lisp/autorevert.el | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/lisp/autorevert.el b/lisp/autorevert.el
index 7cd5e7ee8b..37cf997c4e 100644
--- a/lisp/autorevert.el
+++ b/lisp/autorevert.el
@@ -858,8 +858,12 @@ the timer when no buffers need to be checked."
                   (auto-revert-remove-current-buffer))
               (when (auto-revert-active-p)
                 ;; Enable file notification.
+                ;; Don't bother creating a notifier for non-file buffers
+                ;; except for Dired, since that mode works well with notifiers.
                 (when (and auto-revert-use-notify
-                           (not auto-revert-notify-watch-descriptor))
+                           (not auto-revert-notify-watch-descriptor)
+                           (or buffer-file-name
+                               (eq major-mode 'dired-mode)))
                   (auto-revert-notify-add-watch))
                 (auto-revert-handler)))))
 	(setq bufs (cdr bufs)))
-- 
2.20.1 (Apple Git-117)


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