The project will be cloned and the release tar will be build from it.
Go into the release folder and execute:
docker build --build-arg branch={some_branch} --build-arg version={version_number} --output ../build .
This will generate from the some_branch branch something like invitation_version_number.tar in the build folder.
This file can now be used in a release, or/and be extracted after which you can copy the invitation folder straight into the apps folder. The app should then be ready to be activated.