Do not push any code to that repository.
How to publish

    On https://github.com/nextcloud, tag appropriate commit on the source repository
    Push the new tag to this repository
    Create release on this repository

Automatic package and publish

    Make sure you have the necessary workflow on your https://github.com/nextcloud source repository
    Make sure your tagged commit also have the workflow
    Make sure this repository have the proper APP_PRIVATE_KEY secret set
    Make the nextcloud_release_service user is a co-maintainer of your app on https://apps.nextcloud.com/
    Make sure you have admin rights to this repository