New BF collector Skipper implementation prematurely optimizes

[cstamas]

Affected version

All with BF 1.9+

Bug description

And hence, version selection strategy other than "nearest" is not usable with it (to work, one must use old DF or new BF w/ skipper disabled).

[cstamas]

@caiwei-ebay
See #1565 as Maven is now getting "highest" as alt version selection strategy. It works ONLY if DF or BF w/ skipper disabled, as otherwise BF w/ skipper enabled produces incomplete (prematurely optimized) graph assuming "nearest" selection.

[caiwei-ebay]

@cstamas

With the nearest resolution strategy, Maven was trying to walk thought the entire dependency tree to figure out which dependency version should be picked up, and hence skipper is introduced to skip some dependency resolution if we already know some dependency is already the winner.

Now with the highest resolution strategy, Maven still need to walk thought the entire dependency tree to figure out which dependency version should be picked up? If yes, then need some changes for the skipper solution.

[cstamas]

The simplest would be to make the skipper matching configurable: GACE (version less, as today) vs GACEV (prevent the same subtree again).

Right now, BF works and produce expected results if the skipper is fully disabled.