Patchwork Patcher is a set of tools for transforming and patching Forge mod jars into jars that are directly loadable by Fabric Loader. It does the following things currently:
Remaps Minecraft from official (proguard's obfuscated names) to srg (MCP's runtime mappings)
Remaps the mod jar from srg to official using Tiny Remapper with the srg minecraft jar on the classpath
Remaps the mod jar from official to intermediary using Tiny Remapper with the official minecraft jar on the classpath
Converts the Forge mods.toml manifest to a fabric.mod.json file
Converts @OnlyIn annotations to @Environment for Fabric
Strips @ObjectHolder annotations, removes the field's final modifiers, and creates Consumers that set the fields
Strips @Mod.EventBusSubscriber and @SubscribeEvent annotations and generates event handlers (that handle events) and event registrars (that register event handlers on behalf of a class)
Generates a class implementing ForgeInitializer that registers all the object holders and event registrars
1.16.4 only.
Patchwork Patcher generates jars that require a Fabric mod acting as a compatibility layer to run. Patchwork API fulfills this role, most development will happen there.