bug#19102: 24.4; outline-move-subtree-up/down error at last and second-last subtree

[Stephen Berman <stephen.berman@gmx.net>]

On Thu, 20 Nov 2014 18:21:03 +0200 Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Stephen Berman <stephen.berman@gmx.net>
>> Cc: Eli Zaretskii <eliz@gnu.org>,  19102@debbugs.gnu.org
>> Date: Thu, 20 Nov 2014 11:08:13 +0100
>> 
>> outline-move-subtree-up/down works if there's an empty line after
>> the last subtree, but if not, it puts the last two subtree headers
>> on the same line.
>
> Does it make sense to fix outline-move-subtree-up/down so that they
> also work when there's no empty line after the last subtree?  That's

It didn't occur to me before, but your question prompted me to check and
I see outline-mode derives from text-mode, which sets
require-final-newline to mode-require-final-newline, so I guess the
assumption is indeed that files in outline-mode should end in a newline.

> one thing that looks inelegant in your patch, and might also cause
> some (minor) trouble: what if the user types C-g before this function
> finishes?

We could avoid the trouble by wrapping the newline call in
unwind-protect, couldn't we?  But can C-g really take effect here?
There is no place in the function where execution halts to wait for user
feedback.  Maybe with an outline containing an enormous number of
subtrees the calculations could take long enough to make C-g interrupt
it, though I tried and failed to do it moving over 500 subtrees.  But I
guess those are idle speculations, it does seem that just keeping a
final newline added by the function is the simplest (and perhaps best)
fix, so I guess we should commit some version of that fix and see if
anyone complains.

Steve Berman