I have project A and project B.
I use a GCP Cloud Source Repository on project A as my 'origin' remote.
I use Cloud Build with a trigger on changes to the 'develop' branch of the repo to trigger builds. As part of the build I deploy some stuff with the gcloud builder, to project A.
Now, I want to run the same build on project B. Maybe the same branch, maybe a different branch (i.e. 'release-*'). In the end want to deploy some stuff with the gcloud builder to project B.
The problem is, when I'm on project B (in Google Cloud Console), I can't even see the repo in project A. It asks me to "connect repository", but I can only select GitHub or Bitbucket repos for mirroring. The option "Cloud Source Repositories" is greyed out, telling me that they "are already connected". Just evidently not one from another project.
I could set up a new repo on project B, and push to both repos, but that seems inefficient (and likely not sustainable long term). The curious thing is, that such a setup could easily be achieved using an external Bitbucket/GitHub repo as origin and mirrored in both projects.
Is anything like this at all possible in Google Cloud Platform without external dependencies?
I also tried running all my builds in project A and have a separate trigger that deploys to project B (I use substitutions to manage that), but it fails with permission issues. Cloud Builds seem to always run with a Cloud Build service account, of which you can manage the roles, but I can't see how I could give it access to another project. Also in this case both builds would appear indistinguishable in a single build history, which is not ideal.