Sonic Advance 2 might be late enough that developers started to take that seriously, e.g. I recall hearing that earlier games like Ocarina of Time already were being developed using CVS, for instance, and another game from around that time that I specifically recall would be Pokemon Diamond & Pearl, developed in an SVN repository
This may be true, but since the game was published by THQ in the west who then went bankrupt, no one knows who owns the rights to this game and so no one is likely to ever release it. If source was ever released we still wouldn't use it in the decompilation since that then becomes much more of a legal issue.
