To initialize your local repository, download tree/kernel and other stuff use this ninja command:
mkdir los17 && cd los17 && git clone https://github.com/snakehugo73/scripts.git -b lineage-17.1 && repo init -u https://github.com/LineageOS/android.git -b lineage-17.1 && mkdir .repo/local_manifests && cp scripts/roomservice.xml .repo/local_manifests/ && . scripts/sync.sh && make clobber