containers – How to configure git repo for Node-Red “projects”

I want to create a base container image (docker) of Node-Red, using the “projects” feature (git integration). I want to be able to deploy that image to run with a specified repository, rather than having to use the wizard. But the repository will be configurable so the same image can be used to connect to any node-red project repo.
As it is, I only know how to connect to the git repo by launching the node-red UI, and then using the projects wizard to choose the git repo.
I’m using Node-Red v2. Thanks!