bug#56393: Actually fix the long lines display bug

[Eli Zaretskii]

> Date: Tue, 19 Jul 2022 21:40:36 +0000
> From: Gregory Heytings <gregory@heytings.org>
> cc: gerd.moellmann@gmail.com, larsi@gnus.org, 56393@debbugs.gnu.org
> 
> > Would it help if the tick were incremented by the number of inserted (or 
> > deleted or replaced) characters (perhaps limited by some reasonable 
> > value, like 1000)?  That would be an easy change, and I don't think it 
> > would break anything, since no current code relies on the exact value of 
> > the tick, and the value you get after some non-trivial operation on a 
> > buffer is generally unpredictable anyway. Would that make the tick 
> > usable for this task?
> 
> It would.  In fact it is not even necessary to record the exact number of 
> inserted/deleted/replaced characters.
> 
> > If you agree, I can make such a change (but feel free to do it 
> > yourself).
> >
> 
> I just did it, is this what you had in mind?  The tick is incremented 
> logarithmically.

Yes, thanks.  Perhaps add a comment inside modiff_incr explaining why
we do it logarithmically.  Otherwise, LGTM.

(Hmm... should we say something about this in NEWS?  Not that I expect
some code out there depend on the exact increments in MOFIFF...)