MinecraftForge/MinecraftForge — pull request #27 by immibis (2012-03-31 10:47:33+00:00)
Title: Better ID handling hooks

Mods can use this system to store all their IDs in one, per-world file, change IDs at runtime when switching worlds, transparently copy IDs from servers to clients, and auto-assign IDs (also per-world).
Mods do need to be modified to use the new system; old mods should be unaffected but their IDs will have to be manually managed as before.
Currently works on item and block IDs.