bug#25642: 26.0.50; Save unmodified buffers not visiting a file yet

[Eli Zaretskii <eliz@gnu.org>]

> From: Tino Calancha <tino.calancha@gmail.com>
> Date: Tue, 07 Feb 2017 23:08:42 +0900
> 
> emacs -Q
> C-x b foo
> foo ; Insert something.
> M-: (set-buffer-modified-p nil) RET
> C-x C-s ; No file is written.
> 
> It's easy to change that flag for several buffers
> with `Buffer-menu-not-modified' or
> `ibuffer-do-toggle-modified'.  Then, if you plan to save those
> buffers and if they have buffer-file-name nil, then you
> are not offered to save them.
> 
> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
> >From 2e0d336c4889fac79e5621be34e9149eb3064cce Mon Sep 17 00:00:00 2001
> From: Tino Calancha <tino.calancha@gmail.com>
> Date: Tue, 7 Feb 2017 22:53:35 +0900
> Subject: [PATCH] Save unmodified buffers not visiting a file yet
> 
> * lisp/files.el (save-buffer): Set modified flag non-nil before
> 'basic-save-buffer' call (Bug#25642).

Please don't, at least not unconditionally.  I use this feature all
the time, e.g. when composing email messages.

I don't actually understand why this would be a problem: the user
explicitly wanted to reset the modified status of a buffer, why should
Emacs second-guess what the user meant?  But if there are some use
cases where you find this annoying (please describe them), let's make
this an optional behavior, off by default.

Thanks.