[darcs-users] WhichChanges?

[Florent Becker]

Hi list,

I'm currently struggling to make Darcs.SelectChanges a nicer place to hack,
and i'd especially like to separate UI from patch dependency logic. It's
going fairly well, but I don't feel especially confident in my
understanding of why we need all four cases of the WhichChanges datatype.

I understand that we sometimes want to select the last patches among
the "candidate patches", and sometimes the first, but i'm not sure why we
want them sometimes reversed and sometimes not.

Also, it apparently is a bug to match against patches when they are in Last
or FirstReversed order. Why is that? It seems our matches work on patches
meta-data, so they should be immune to reversing and reordering patches.
Why don't we generalise the iswanted function the obvious way?

Thanks for your answers,

Florent