Verify that all-jobs-succeeded CI job depends on all other jobs

[joshlf]

Due to a limitation in GitHub's merge queue support, we need to manually list all jobs that are required to pass before a PR in the merge queue can be considered to have succeeded. In order to avoid having to list all jobs manually in the GitHub settings page for this repository, we instead provide the following job which depends on all other jobs:

zerocopy/.github/workflows/ci.yml

Lines 445 to 453 in 68953ed

	# Used to signal to branch protections that all other jobs have succeeded.
	all-jobs-succeed:
	name: All checks succeeded
	if: success()
	runs-on: ubuntu-latest
	needs: [build_test, kani, check_fmt, check_readme, check_msrv, check_versions, generate_cache]
	steps:
	- name: Mark the job as successful
	run: exit 0

This works, but is still error-prone: there's nothing that ensures that this job won't fall out of sync if we add new CI jobs in the future.

Similar to jobs like check_versions, we should write a new CI job that automatically extracts all jobs which should block a PR merging, and make sure that all-jobs-succeed depends on each such job.

Mentoring instructions

The job should support the following behaviors:

• Enumerate every YAML file under .github
  • NOTE: Both .yml and .yaml are possible file extensions
• For each such file:
  • Parse it as YAML with yq
  • Extract any jobs which run for each PR (at a minimum, it must support this syntax, but you should also confirm that there aren't other ways of indicating to GitHub that an action should be run for each PR)
• Ensure that all-jobs-succeeded depends on each job found in the previous step

[tommy-gilligan]

This issue is in the latest This Week in Rust. I would like to help if that's OK

[joshlf]

Sounds good, I'll assign it to you, thanks! Let me know ow if you have any questions or run into any issues.

[tommy-gilligan]

I'm happy using yq but AFAICT it is something that will need to be installed and it is not included in CI's apt repository.
Luckily there are many ways to install it outside of apt https://github.com/mikefarah/yq/#install . Do you have a preference?

Alternatively:

• use more basic ubiquitous tools eg. awk/sed/grep (downside is that these tools do not really 'get' YAML) or
• use a small Rust tool as part of CI ie. xtask

[tommy-gilligan]

I've gone with using go install for now