workflows/{labels,reviewers}: fix concurrency groups for nested workflows

[wolfgangwalther]

This didn't work as intended. When a workflow is run with workflow_call, it will have github.workflow set to the parent workflow. So the caller input that we passed, resulted in this concurrency key:

Eval-Eval-...

But that's bad, because the labels and reviewers workflows will cancel each other!

What we actually want is this:

• Label and Reviewers workflow should have different groups.
• Reviewers called via Eval and called directly via undraft should have different groups.

We can't use the default condition we use everywhere else, because github.workflow is the same for Label and Reviewers. Thus, we hardcode the workflow's name as well. This essentially means we have this as a key:

<name-of-running-workflow>-<name-of-triggering-workflow>-<name-of-event>-<name-of-head-branch>

This should do what we want.

Things done

• Fits CONTRIBUTING.md, pkgs/README.md, maintainers/README.md and other contributing documentation in corresponding paths.

---

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[MattSturgeon]

Different users could have the same head branch name in their forks and run CI for their PRs at the same time.

I assumed that head_ref would be refs/pull/1234/head. Is it actually the branch name? 👀

[wolfgangwalther]

Yes, apparently. See for example the summary page here, section annotations: https://github.com/NixOS/nixpkgs/actions/runs/15634880254?pr=413785

There you can see the actual concurrency key used.

[philiptaron]

Thank you for becoming an expert at this, @wolfgangwalther.

[nixpkgs-ci]

Backport failed for release-24.11, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin release-24.11
git worktree add -d .worktree/backport-416448-to-release-24.11 origin/release-24.11
cd .worktree/backport-416448-to-release-24.11
git switch --create backport-416448-to-release-24.11
git cherry-pick -x 7ba7720b28cc03d44d5ad1f5931ad4a88e068470 6793e238faeffcb58f1f6e1241c7390649fb8197

[nixpkgs-ci]

Backport failed for release-25.05, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin release-25.05
git worktree add -d .worktree/backport-416448-to-release-25.05 origin/release-25.05
cd .worktree/backport-416448-to-release-25.05
git switch --create backport-416448-to-release-25.05
git cherry-pick -x 7ba7720b28cc03d44d5ad1f5931ad4a88e068470 6793e238faeffcb58f1f6e1241c7390649fb8197