workflows: migrate to GitHub Container Registry.

[MikeMcQuaid]

This seems a better fit for us (unauthenticated anonymous access) than GitHub Packages Docker registry was.

Followed steps on https://docs.github.com/en/packages/getting-started-with-github-container-registry/migrating-to-github-container-registry-for-docker-images

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same change?
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes? Here's an example.
• Have you successfully run brew style with your changes locally?
• Have you successfully run brew tests with your changes locally?

---

[MikeMcQuaid]

@sjackman @jonchang This won't actually push any changes as-is until tagged or on the master branch. Will merge when you're 👍🏻 and fix/revert depending on the master builds. Might be nice to get this in for 2.5.0 so we can announce it there.

[sjackman]

https://docs.github.com/en/packages/getting-started-with-github-container-registry/migrating-to-github-container-registry-for-docker-images#domain-changes

docker.pkg.github.com/OWNER/REPOSITORY/IMAGE_NAME
ghcr.io/OWNER/IMAGE_NAME

Notice that it's not ghcr.io/OWNER/REPOSITORY/IMAGE_NAME but instead ghcr.io/OWNER/IMAGE_NAME, so ghcr.io/homebrew/brew/… needs to change to ghcr.io/homebrew/… throughout.

[maxim-belkin]

It also needs a new PAT as it can't use GITHUB_TOKEN:

GitHub Container Registry does not support using GITHUB_TOKEN for your PAT so you must use a different custom variable, such as CR_PAT. For more information, see "Creating and storing encrypted secrets."

[MikeMcQuaid]

Notice that it's not ghcr.io/OWNER/REPOSITORY/IMAGE_NAME but instead ghcr.io/OWNER/IMAGE_NAME, so ghcr.io/homebrew/brew/… needs to change to ghcr.io/homebrew/… throughout.

Done!

[MikeMcQuaid]

It also needs a new PAT as it can't use GITHUB_TOKEN

Done!

Changes addressed

[MikeMcQuaid]

Let's see how this goes 🤞🏻

[MikeMcQuaid]

Working (finally): https://github.com/Homebrew/brew/runs/1066866856#step:24:1