bug#13949: 24.3.50; `fill-paragraph' should not always put the buffer as modified

[Eli Zaretskii <eliz@gnu.org>]

> Date: Thu, 14 Mar 2013 08:57:35 +0100
> From: Dani Moncayo <dmoncayo@gmail.com>
> Cc: 13949@debbugs.gnu.org
> 
> In general, I think that a command should flag the buffer as modified
> only when the buffer contents at the end of the command were different
> from the contents at the beginning of that  same command.

Then your wish is much broader than the original bug report says.
E.g., you'd like the following to leave the buffer marked as
unmodified, right?

  emacs -Q
  M-<
  C-d
  ;

Or how about this:

  emacs -Q
  M-x overwrite-mode RET
  M-<
  ;

fill-paragraph first removes all the newlines from the paragraph, and
then inserts only as many as needed to get a filled paragraph.  So the
buffer gets changed at least twice in the process.

> But, I don't know complex is that to implement, and perhaps that
> complexity outweighs the benefits.

Stefan answered that.  I'll write there why I think it might not be a
good idea.