[Freeciv-Dev] (PR#13153) Alliances and stacking

["Per I. Mathisen" <per@xxxxxxxxxxx>]

<URL: http://bugs.freeciv.org/Ticket/Display.html?id=13153 >

A few years ago (and unwisely just before a release) I added allied
ferrying to the code, so that allies can ship each other's units. This led
to a long chase after obscure and rare bugs in the code, which ended only
years later. In retrospect, I regret implementing this. It led to a lot of
complications in the rules and in the code that were not necessary.

In fact, I think allied stacking as such is a misfeature. It leads to a
lot of complicated rules to deal with it, and a lot of very bug prone
code. For example, when an alliance is broken, units that suddenly find
themselves stacking illegally are teleported all around the map. This is
very ugly.

So I think that removing the option of allied stacking and being inside
allied cities may clean up the rules and make them better. This will
remove the need to teleport units around (a horrible kludge) for treaty
changes.

It allows us to dispense with the complicated attack rules for which
stacks you may attack, depending on the mix of unit ownership in the
stack. It removes the possibility of hiding enemy units underneath neutral
units.

It makes resolving city ownership changes much easier, since the case of
mixed ownership unit stackeds is then a nightmare, especially if you are a
ferry ferrying units owned by another player...

It also allows us to implement owned fortresses, like in Warlords, where
the last unit to visit it 'owns' it, without bothering about complications
like 'what if two units of different owners are on the same square'. This
is wanted for a better borders implementation
(http://www.freeciv.org/index.php/Borders).

Opinions?

  - Per