bug#31039: 27.0.50; allow silencing auto-save

[Eli Zaretskii <eliz@gnu.org>]

> From: Noam Postavsky <npostavs@gmail.com>
> Date: Sun, 05 Aug 2018 22:43:16 -0400
> Cc: aaronjensen@gmail.com, 31039@debbugs.gnu.org
> 
> I've prepared a patch to add this feature (see attached file). Since
> this is my first contribution to this project (and also my first time
> sending a patch via email), it's possible I've made some mistakes
> along the way. Any feedback is appreciated.

Thanks.

> * src/keyboarc.c (auto_save_quiet): New variable, allows suppressing
        ^^^^^^^^

A typo.

> diff --git a/doc/emacs/files.texi b/doc/emacs/files.texi
> index a7cc57e4e9..0635aeba71 100644
> --- a/doc/emacs/files.texi
> +++ b/doc/emacs/files.texi
> @@ -1023,11 +1023,12 @@ Auto Save
>  
>    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-quiet} 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.  Errors occurring during auto-saving
> +are caught so that they do not interfere with the execution of commands
> +you have been typing.

Each variable (and function and command and macro and ...) described
in the manual must be indexed.  So please add

  @vindex auto-save-quiet

before this paragraph.

Also, this text should say what is the default of this variable.

Btw, I'd prefer to call the variable auto-save-no-message.
auto-save-quiet might not make its intent clear enough, IMO.

Thanks.