Add include this repository from your local_manifests inside .repo/local_manifests/
<?xml version="1.0" encoding="UTF-8"?>
<manifest>
<remote name="apinela"
fetch="https://github.com/apinela/" />
<project path="vendor/extra" name="android_vendor_extra" remote="apinela" revision="aosp-8.1" />
</manifest>