bug#23794: Emacs 25.0.94: Patch to make sort-lines respect visible lines (fairly urgent)

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sat, 18 Jun 2016 20:49:12 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 23794@debbugs.gnu.org
> 
> > For clarity, the original behavior of sort-lines is what the patch restores. The backward-incompatibility to which
> > you refer is then just an implementation error that occurred when switching over to the overlay implementation
> > of outlines as there was never any documentation that I can see that suggested any behavior change. There
> > certainly could be better documentation as to whether a 'line' refers to a visible line, an invisible line or both
> > but many functions do not delineate this. A major reason for making lines invisible is so that they are not
> > treated as regular lines when functions are applied to buffer text. Thus, sort-lines should by default operate on
> > visible lines. It could be extended or another function could be written to operate on invisible lines as well, e.g.
> > sort-invisible-lines and an alias could be made to sort-lines to be called sort-visible-lines. All of this in the
> > future. The only thing I am suggesting for right now is to restore the original behavior. Note that if all lines are
> > visible, the patch codes works as well. The issue is that when lines are invisible the current code in Emacs
> > does not work in a very useful way.
> 
> I think I already responded to this argument in my previous message.

In case it wasn't clear, I would welcome a change that is specific to
outline modes, whereby sorting would produce the same effect as it did
in Emacs 21 in these modes.  But even in outline modes, I think there
should be a way of getting the old behavior back.