A main class wrapper for Minecraft Forge that bundles multiple file paths to one mod's contents into one URL.

It uses the original MOD_CLASSES environment variable present in Forge for Minecraft ≤1.19.2 with the same format to support build tools without major changes.

1. Set the unionRelauncher.mainClass system property to point to the original main class.
2. Set up the MOD_CLASSES environment variable with an id-path list.
   • The environment variable is a list of entries separated by File.pathSeparator.
   • Each entry is one of:
     • a file path belonging to the default mod
     • an id-path pair id%%path, where id is a unique id for the mod path group and path is the file path belonging to that mod
3. Launch the Union Relauncher module or jar.