bug#22295: viper-mode undo bug introduced between Nov 10 and Nov 14

[Phillip Lord]

Eli Zaretskii <eliz@gnu.org> writes:

>> Cc: phillip.lord@russet.org.uk, 22295@debbugs.gnu.org
>> From: Michael Kifer <kifer@cs.stonybrook.edu>
>> Date: Mon, 16 May 2016 13:14:05 -0400
>> 
>> >  Another alternative is to make viper use the default Emacs undo, and
>> > then ask you and other users of viper to tell where the results don't
>> > match your expectations.  It could well be that starting with a clean
>> > slate will get us to the goal faster and with less complex code.
>> 
>> This would be a non-starter and would cause a mass migration to vim. The 
>> undo would also then be
>> implementation dependent. If, say, "delete 2 words" is implemented 
>> differently from how it is now then it would
>> be undone via a different sequence of commands. 
>
> Then I guess the current trial-and-error method will have to be the
> way.  Too bad, I have hard time believing we will be ready with a
> complete solution in time for Emacs 25.1, which is what I hoped.

I worry about this as well. I still do not understand why my changes
have caused this problem; I'd rather not be taking the approach to
redoing the implementation of viper during release candidate.

Still, if, as I suspect, it's because the timing of boundaries has
changed slightly, it's likely to be the only choice.

Phil