Add different MAME sets

[RobLoach]

No description provided.

[markwkidd]

Howdy! Thanks for tuning in to MAME scanning with me :)

I am hoping that the standard XML DATs in the metadat folder can serve a few purposes and would be useful for users trying to validate their sets for RetroArch use even if built-in scanning is not adjusted for MAME.

That said, I am really hoping to help add a new database scanning mode that can accommodate arcade ROM sets. I have attempted to move the discussion forward regarding how to make that work by creating a new Development forum thread that you might want to take a look at: https://forums.libretro.com/t/specification-for-arcade-rom-scanning/8624/

For some unknowable reason I have spent the last few months off and on becoming very well acquainted with MAME ROM validation -- moreso than I am acquainted with how a new scanning mode might be added. For any given MAME or FB Alpha ROM set, there can be six different totally valid ZIP files and the same number of valid .7z archives. CRC scanning doesn't make sense in that context -- it's too different from the 'native' validation approach used by MAME.

[i30817]

The only way to deal with mame sets is imo to scan zips not the roms inside of it. And scan only a particular kind of standardized zip: those that have been standardized by trrzip (or whatever that utility that's necessary to have torrents agree on zip files is).

I'd suggest expanding the current limitation to merge set to both merge set and split set by simply only scanning the 'main' zips of a split set (not bios, not 'non-game' separate parts, just the part that uniquely identifies a game version).

I think they basically have the same name (on the zips) as the merge set so i don't see why the merge set list of names couldn't be used to validate which roms to include on a data for the split set. RA would have no guarantee that the game is 'complete' but that's not its job anyway, just recognizing 'this is this game, for sure', which these crcs do.