bug#31039: 27.0.50; allow silencing auto-save

[Federico <federicotedin@gmail.com>]

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Noam, Eli: I've applied the fixes you have both mentioned. I ended up
using DEFVAR_BOOL to create the variable, but I'm not sure I used the
variable correctly when calling Fdo_auto_save (the function only takes
Lisp_Object). I have attached a new patch.

Regarding the copyright assignment, mine was approved one or two weeks ago.

Thanks

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From 8ab8141e70c8d0f97f9bd265275f6ef1a043317c Mon Sep 17 00:00:00 2001
From: Federico Tedin <federicotedin@gmail.com>
Date: Mon, 6 Aug 2018 19:53:05 -0300
Subject: [PATCH] Add variable auto-save-no-message

* src/keyboard.c (auto_save_no_message): New variable, allows suppressing
  auto-saving message.
* lisp/cus-start.el (standard): Add auto-save-no-message variable.
* doc/emacs/files.texi: Update manual.
* etc/NEWS: Update news.
---
 doc/emacs/files.texi | 13 ++++++++-----
 etc/NEWS             |  4 ++++
 lisp/cus-start.el    |  1 +
 src/keyboard.c       |  8 ++++++--
 4 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/doc/emacs/files.texi b/doc/emacs/files.texi
index a7cc57e4e9..362993c02e 100644
--- a/doc/emacs/files.texi
+++ b/doc/emacs/files.texi
@@ -1021,13 +1021,16 @@ Auto Save
 called @dfn{auto-saving}.  It prevents you from losing more than a
 limited amount of work if the system crashes.
 
+@vindex auto-save-no-message
   When Emacs determines that it is time for auto-saving, it considers
 each buffer, and each is auto-saved if auto-saving is enabled for it
-and it has been changed since the last time it was auto-saved.  The
-message @samp{Auto-saving...} is displayed in the echo area during
-auto-saving, if any files are actually auto-saved.  Errors occurring
-during auto-saving are caught so that they do not interfere with the
-execution of commands you have been typing.
+and it has been changed since the last time it was auto-saved.  When
+the @code{auto-save-no-message} variable is set to @code{nil}, the message
+@samp{Auto-saving...} is displayed in the echo area during auto-saving,
+if any files are actually auto-saved.  The default value for
+@code{auto-save-no-message} is @code{nil}.  Errors occurring during auto-saving
+are caught so that they do not interfere with the execution of commands you
+have been typing.
 
 @menu
 * Files: Auto Save Files.       The file where auto-saved changes are
diff --git a/etc/NEWS b/etc/NEWS
index 21887f5bfd..49d5afbca9 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -189,6 +189,10 @@ from a remote host.
 This triggers to search the program on the remote host as indicated by
 'default-directory'.
 
++++
+** New variable 'auto-save-no-message'.
+When set to t, no message will be shown when auto-saving (default value: nil).
+
 \f
 * Editing Changes in Emacs 27.1
 
diff --git a/lisp/cus-start.el b/lisp/cus-start.el
index f31d1df309..0d4b968748 100644
--- a/lisp/cus-start.el
+++ b/lisp/cus-start.el
@@ -345,6 +345,7 @@ minibuffer-prompt-properties--setter
 	     ;; keyboard.c
 	     (meta-prefix-char keyboard character)
 	     (auto-save-interval auto-save integer)
+             (auto-save-no-message auto-save boolean)
 	     (auto-save-timeout auto-save (choice (const :tag "off" nil)
 						  (integer :format "%v")))
 	     (echo-keystrokes minibuffer number)
diff --git a/src/keyboard.c b/src/keyboard.c
index 7ab9a6069a..66041f317b 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -2626,7 +2626,7 @@ read_char (int commandflag, Lisp_Object map,
       && num_nonmacro_input_events - last_auto_save > max (auto_save_interval, 20)
       && !detect_input_pending_run_timers (0))
     {
-      Fdo_auto_save (Qnil, Qnil);
+      Fdo_auto_save (auto_save_no_message ? Qt : Qnil, Qnil);
       /* Hooks can actually change some buffers in auto save.  */
       redisplay ();
     }
@@ -2691,7 +2691,7 @@ read_char (int commandflag, Lisp_Object map,
 	  if (EQ (tem0, Qt)
 	      && ! CONSP (Vunread_command_events))
 	    {
-	      Fdo_auto_save (Qnil, Qnil);
+	      Fdo_auto_save (auto_save_no_message ? Qt : Qnil, Qnil);
 	      redisplay ();
 	    }
 	}
@@ -11391,6 +11391,10 @@ result of looking up the original command in the active keymaps.  */);
 Zero means disable autosaving due to number of characters typed.  */);
   auto_save_interval = 300;
 
+  DEFVAR_BOOL ("auto-save-no-message", auto_save_no_message,
+	       doc: /* Non-nil means do not print any message when auto-saving. */);
+  auto_save_no_message = false;
+
   DEFVAR_LISP ("auto-save-timeout", Vauto_save_timeout,
 	       doc: /* Number of seconds idle time before auto-save.
 Zero or nil means disable auto-saving due to idleness.
-- 
2.17.1