Unpacking does not support conflict rules

[stof]

When unpacking a pack, conflict rules are not unpacked, which might create a different result if there was any.

[nicolas-grekas]

PR welcome.

[nicolas-grekas]

When a conflict rule in a pack conflicts with an existing conflict rule in the main composer.json, we would ideally compute the union of both conflicting rules.

[nicolas-grekas]

Copy/pasting from #645 (comment):

About skipping conflicts, that might be unneeded actually: when packs are installed, the conflicts are taken into account. Now that #651 locks the major version of installed packages when unpacking, this kinda freezes the resolved conflicts. Of course, it's always possible that removing the conflicts will yield a different solution after unpacking, but the window becomes quite narrow. Maybe narrow enough to close #371 and save us from spending time on this.

[nicolas-grekas]

Closing as there is little incentive to work on this.
PR welcome when this incentive is high for you.