How Fruit Trees was built
Raw game files read
blocktypes/plant/fruittreebranch.json
Processing
Fruit trees are a separate worldgen system from regular trees -- one file,
blocktypes/plant/fruittreebranch.json, whose glob-keyed attributes describe every
variety's climate band and the concrete fruit item it produces. There's no separate per-species
generator file the way regular trees have; everything needed is already on this one block type.