Doc updates for buffer-stale-function now applying to file buffers too

* doc/emacs/arevert-xtra.texi (Supporting additional buffers):
* doc/lispref/backups.texi (Reverting):
Update for buffer-stale-function also applying to file-buffers.

* lisp/autorevert.el (auto-revert-buffers):
* lisp/files.el (buffer-stale--default-function)
(buffer-stale-function, revert-buffer--default): Doc tweaks.

* etc/NEWS: Related edits.

1 files changed, 4 insertions, 1 deletions

diff --git a/etc/NEWS b/etc/NEWS
index c3998934b5e..db1dd43216b 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1401,11 +1401,14 @@ argument, with the same interpretation as the returned value of
 
 ** Revert and Autorevert changes
 
-FIXME buffer-stale-function no longer just for non-file buffers?
++++
 *** The default values of `buffer-stale-function', `revert-buffer-function',
 and `revert-buffer-insert-file-contents-function' are no longer nil.
 Instead they default to functions that do what the nil value used to.
 
++++
+*** `buffer-stale-function' is now used for buffers visiting files too.
+
 ---
 *** If Emacs is compiled with file notification support, it uses notifications
 instead of checking file time stamps.  To disable this, set the user option