This project disects jar files into their component parts, and makes a "supermod" jar file that contains the amalgamated assets of every mod.
Then, it replaces every asset in a jar file with files from the supermod. In some cases, they're slightly modified to not cause crashes or glitchy textures.
This is specifically for Minecraft mods.
This requires Python 3.10. There have been some issues with 3.9 in the past.
It is also recommended to install tqdm through pip, although it is not strictly required.
Example:
# Append (or create) to the supermod.jar file all the assets from Mekanism.jar and MekanismGen.jar
python3.10 concat.py supermod.jar Mekanism.jar MekanismGen.jar
# Horribly mangle Quark.jar into Quark.scrambled.jar using the files from supermod.jar, with sanity 0.8 (80% of files stay the same).
python3.10 replace.py -s 0.8 Quark.jar Quark.scrambled.jar supermod.jar