User blog comment:Sinthorion/Vanilla Item / Block obfuscated code name translation/@comment-25612015-20150916193820/@comment-25612015-20150920064656

I've used CFR to decompile the mod.

It has an option called "--extraclasspath (string)" to allow helper jars to be searched for analysis. Although I've not tested it, I think it might do what you want, provided perhaps the Minecraft source code be collected as a big jar file.