You're probably looking for:
https://github.com/EIGHTFINITE/pokeemerald-expansion/tree/master
https://github.com/EIGHTFINITE/pokeemerald-expansion/blob/master/INSTALL.md
https://github.com/EIGHTFINITE/pokeemerald-expansion/blob/master/CHANGELOG.md
Or if you want to start coding:
git init .
git remote add origin https://github.com/EIGHTFINITE/pokeemerald-expansion.git
git remote add RHH https://github.com/rh-hideout/pokeemerald-expansion.git
git fetch --force --all --tags
git checkout -B master refs/remotes/origin/master