Add label if pre-commit passes

[hmellor]

Allows Buildkite to not run CI until pre-commit is passing, saving CI cost.

Originally discussed in https://vllm-dev.slack.com/archives/C07R5PAL2L9/p1736691851928849

[github-actions]

👋 Hi! Thank you for contributing to the vLLM project.
Just a reminder: PRs would not trigger full CI run by default. Instead, it would only run fastcheck CI which starts running only a small and essential subset of CI tests to quickly catch errors. You can run other CI tests on top of those by going to your fastcheck build on Buildkite UI (linked in the PR checks section) and unblock them. If you do not have permission to unblock, ping simon-mo or khluu to add you in our Buildkite org.

Once the PR is approved and ready to go, your PR reviewer(s) can run CI to test the changes comprehensively before merging.

To run CI, PR reviewers can do one of these:

• Add ready label to the PR
• Enable auto-merge.

🚀

[ywang96]

Thanks for doing this!

Does this mean if a PR with ready label does not have pre-commit passed, we will still not run the full CI?

[hmellor]

The idea I have for this is that:

• Fastcheck runs when pre-commit passed is present
• Full CI runs when pre-commit passed and ready are present

It still needs:

• @khluu to pipe it up to Buildkite
• the pre-commit passed label to be created in the repo
• the pre-commit passed label to be removed when a new pre-commit run starts
• maybe something added to the bot comment explaining

This should have significant cost savings on PRs where ready has been added but pre-commit failing code has been pushed.

[russellb]

This seems fine, though I think we could accomplish the same thing in .github/mergify.yml. I only bring it up because that tool is used for other label automation. It would be something roughly like this:

diff --git a/.github/mergify.yml b/.github/mergify.yml
index 43bc5ce62..225d311fc 100644
--- a/.github/mergify.yml
+++ b/.github/mergify.yml
@@ -95,3 +95,23 @@ pull_request_rules:
     label:
       remove:
         - needs-rebase
+
+- name: add 'pre-commit passed' label on successful pre-commit job
+  description: Automatically apply pre-commit passed label
+  conditions:
+    - check-success=pre-commit
+  actions:
+    label:
+      add:
+        - pre-commit passed
+
+- name: remove 'pre-commit passed' label when success status is not present
+  description: Remove pre-commit passed label when not marked as successful
+  conditions:
+    - or:
+      - check-pending=pre-commit
+      - check-failure=pre-commit
+  actions:
+    label:
+      remove:
+      - pre-commit passed

[hmellor]

I originally based this action on add_label_automerge.yml. I don't mind which solution we go with though.