This is based on @vsoch's amazingly useful singularity-deploy template.

Instead of building the SIF directly, my version uses a Dockerfile with the Docker build-push action to upload a Docker image to the GitHub container registry.

Right now you can only have one Dockerfile per repo, until I work out how to use the build-push action to build multiple containers.

The steps are pretty similar to @vsoch's orignal repo:

1. Template or fork.
2. Edit the repo:
   • Check out a new branch
   • Modify the Docker recipe (Dockerfile)
   • Update the Version file
   • Push the new branch to GitHub
3. Open a PR for the new branch. This triggers the test build, which just builds the Docker image but doesn't push it.
4. Once the check passes, merge the PR. This creates a release, re-builds the Docker image and uploads it to GHCR.

Notes

To get the repo to work with GHCR:

• Enable GHCR for your account.
• Use the following URL to create a Personal Access Token with the scopes read:packages, write:packages and delete:packages. https://github.com/settings/tokens/new?scopes=write:packages.
  This is documented here.
• Add the PAT to the Repository Secrets and call it CR_PAT (Settings -> Secrets -> New Repository Secret)

These steps allow the actions runner to authenticate with GHCR and push/pull the images.