To initialize your local repository use
repo init -u https://github.com/nitrogen-project/nitrogen_manifest.git -b mm6.0
Then to sync up:
repo sync
Build command is
./build.sh device -j#
Supported Devices
LG Optimus G - e975, e975k, e975r, e975t, e977, e987, f180s, f180l, f180k, ls970