Refactor package selection

[mpdude]

I find the selectPackages() part very hard to understand or to test.

This PR attempts to break it up into smaller pieces, namely:

• A PackageSelection class which tracks the packages that are to be processed
• A LinkResolver which can follow dependencies from the current PackageSelection and add more packages if needed
• LinkProviders that know which dependencies to follow for a given package
• FilteredPackageSelection which helps in the case of "filtered builds".

Feedback is welcome, but please let's try to focus on fundamental issues before discussing CS glitches.

Thanks!

[stof]

It looks like your work is not build on top of the latest Satis version. Github reports that the PR conflicts with master

[mpdude]

Thanks, fixed.

[naderman]

Yeah I think it's a great idea to refactor this, ideally we'd start having some tests too, if you want to work on those?

[mpdude]

Sure, will see what I can do.

[mpdude]

While we're at it – what's your minimum requirements for merging this?

It happened to me quite a few times that PRs grew so big that nobody really wanted to review them anymore and they never got merged.

I don't think this changes any behavior right now and we can also add tests in another PR.

[naderman]

On satis? I don't really care about the size. But obviously smaller self contained PRs make sense if you can actually split it up in a meaningful way, but otherwise just keep going here. Only issue will be keeping it in sync with other changes.

[naderman]

In general I'm a bit hesitant with merging something like this right now, not because of the size but because of the lack of tests.

[mpdude]

So please help on #184 so we can get the relevant (functional) tests here.

[alcohol]

Closing this due to lack of activity and conflicting state. Please do feel free to re-open and update this PR if said functionality is still desired. :-)