preventing duplicate ISRCs

[JonnyJD]

see also: mineo/mbstuff@c1e90aa

[JonnyJD]

1. We want to prevent submitting an ISRC we found to two different tracks -> prevent clear mistakes on our part -> Error if we find something like that
2. Try to fix/prevent duplicate ISRCs in general, even if we actually don't do anything wrong ourselves -> Only a warning.
3. OPTIONAL: Possibly giving the option to show every track listed for our ISRCs to do some majore collision clean-up. This is something you might only want to do for BIG releases (many tracks per ISRC) and if you have some time to spare. Additionally the edititing/fixing should be done completely in the browser. This is only done because you have a better chance to fix those collisions when you know one ISRC-recording relation for sure.

[JonnyJD]

Number 3 might better be done with web service 2. Then we can actually get all the recordings for one ISRC with one request. Drastically reducing the work for us and the server.

Additionally, there might not be as much ISRC collisions as with PUIDs and most collisions are on one release, probably. We want to solve that with 2.

[JonnyJD]

An example for 1. in my collection is London Calling by The Clash:
http://musicbrainz.org/cdtoc/hSI7B4G4AkB5.DEBcW.3KCn.D_E-
http://forums.musicbrainz.org/viewtopic.php?pid=9159#p9159

I have a DVD-Writer that gives normal result and a DVD-Reader giving GBBBN7902019 for track 3 AND 4.

This is ALSO an example of 2. (before I fix it). Track 18 AND 19 both have the same ISRCS (as my DVD-reader also tries to tell me).