docker: use 24.04 for ghcr.io/homebrew/brew

[cho-m]

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Part of #21761.

Dockerfile default should be no/low impact change as we don't use the default ARG version.

Searching Homebrew org for ghcr.io/homebrew/brew usage: https://github.com/search?q=org%3AHomebrew+ghcr.io%2Fhomebrew%2Fbrew&type=code, seems to only impact:

• .devcontainer/devcontainer.json (developer-specific, low impact)
• Homebrew/brew tests.yml formula-audit, seems safe to run on Ubuntu 24.04:
  

  brew/.github/workflows/tests.yml

  Lines 115 to 137 in 4b1bc6b

  	formula-audit:
  	name: formula audit
  	needs: syntax
  	if: github.repository_owner == 'Homebrew' && github.event_name != 'push'
  	runs-on: ubuntu-latest
  	container:
  	image: ghcr.io/homebrew/brew:main
  	steps:
  	- name: Set up Homebrew
  	id: set-up-homebrew
  	uses: Homebrew/actions/setup-homebrew@main
  	with:
  	core: true
  	cask: false
  	- name: Run brew readall on homebrew/core
  	run: brew readall --os=all --arch=all --aliases homebrew/core
  	- name: Run brew audit --skip-style on homebrew/core
  	run: brew audit --skip-style --except=version --tap=homebrew/core
  	- name: Generate formula API
  	run: brew generate-formula-api --dry-run

[Copilot]

Pull request overview

Updates the Homebrew Docker image defaults so the canonical ghcr.io/homebrew/brew tags track Ubuntu 24.04, aligning the published “brew” image with the ongoing Ubuntu 24.04 migration work.

Changes:

• Switch the Dockerfile default base image version from Ubuntu 22.04 to 24.04.
• Update the Docker publishing workflow so ghcr.io/homebrew/brew:{latest,<version>,main} tags are generated only for the 24.04 build.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
Dockerfile	Changes the default ARG version to 24.04 so local/default builds use Ubuntu 24.04.
.github/workflows/docker.yml	Moves the ghcr.io/homebrew/brew:* tagging conditions from 22.04 to 24.04 for release and main pushes.

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[MikeMcQuaid]

As long as this doesn't change the default homebrew/core image: seems fine!

[MikeMcQuaid]

Does this change the Homebrew/homebrew-core default CI image?

[cho-m]

No, this only impacts container label ghcr.io/homebrew/brew which we currently don't use in Homebrew/homebrew-core.

As far as I'm aware, bottling runners is a mix of:

• https://github.com/Homebrew/homebrew-core/blob/main/.github/workflows/tests.yml
• https://github.com/Homebrew/homebrew-core/blob/main/.github/workflows/dispatch-build-bottle.yml#L85-L88
• https://github.com/Homebrew/homebrew-core/blob/main/cmd/determine-rebottle-runners.rb#L24-L30
• https://github.com/Homebrew/brew/blob/main/Library/Homebrew/github_runner_matrix.rb#L101-L104

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A bit messy as we currently have to update multiple locations. Maybe we should be using a dedicated/unversioned container label for bottling so we don't have to worry about these being updated in-sync.

[cho-m]

Maybe we should be using a dedicated/unversioned container label for bottling so we don't have to worry about these being updated in-sync.

If we want to use ghcr.io/homebrew/brew:main for this, then can close this PR and handle as part of Ubuntu migration PR.

[cho-m]

Actually I prefer the idea of switching workflows to use this container label/tag as the maintenance is a pain trying to modify a couple dozen files.