Merge in importer.

[DArtagan]

When duplicate records are found during import, the user has the option to merge the two sets together. Presently, only works when tracks don't conflict.

This is not the final commit, I'm planning on resolving track conflicts before this is ready for merging. Before I head down that road though, I'd really like my work double-checked (@sampsyo). This project is impressively large, I did my best to understand this portion, but I'm not sure if I'm abusing the database or pipeline or something.

Cheers!

P.S. Related to issue #112

[DArtagan]

@sampsyo a few questions:

• In for the unittests, I wanted to test merging against an album with multiple tracks. Making a list of a couple TrackInfo objects only seems to ever have the first one picked up, why?
• I'd like to also allow for interactive merging, where two albums contain overlapping parts of each other. My first thought is to compare the track ids, would you agree with this approach? Would mocks be the proper way to unittest such interactions?
• I'm not sure why the builds are failing on test.test_mb.MBLibraryTest.test_match_album. It built fine when I committed last weekend, but not this weekend? All 37 tests in test_mb.py pass on my machine.
• I see you're running AppVeyor in addition to Travis CI. What do you think of it?

[sampsyo]

Hi! Thank you for writing this! It looks amazing, and it fulfills something that many people have asked for. And I'm very very sorry that I didn't get around to this earlier—thanks for your patience while I caught up on the backlog.

I'll review the code now. To answer your questions:

In for the unittests, I wanted to test merging against an album with multiple tracks. Making a list of a couple TrackInfo objects only seems to ever have the first one picked up, why?

I'm not 100% sure what's going on here—are you referring to the new test_merge_duplicate_album_without_duplicate_tracks, but with the commented-out lines commented back in? If so, should I just run that to see what you're talking about?

I'd like to also allow for interactive merging, where two albums contain overlapping parts of each other. My first thought is to compare the track ids, would you agree with this approach?

Is the idea to let you break apart an album and then merge part of it into a new album? That sounds like a rather complex thing to orchestrate. Would you mind terribly much if we left that extension until after we finish this more basic version?

Would mocks be the proper way to unittest such interactions?

Probably—depending on where the user input comes in.

I'm not sure why the builds are failing on test.test_mb.MBLibraryTest.test_match_album. It built fine when I committed last weekend, but not this weekend? All 37 tests in test_mb.py pass on my machine.

That's not your fault, and now fixed. Nothing to worry about!

I see you're running AppVeyor in addition to Travis CI. What do you think of it?

So far so good; it seems to do its job admirably, and it's great that it's free for open source. It's disabled for us, unfortunately, because we haven't gotten all the tests passing on Windows quite yet (#670).

[sampsyo]

Style nitpick: for comments like this, please use a period at the ends of sentences.

[DArtagan]

Mad props to udibox1209, making this happen in #2725.