Add concurrency control to cancel in-progress PR workflows

[TTOzzi]

When updating a pull request that's already open, each new commit can trigger a workflow. If the PR author doesn't have permission to cancel workflows, this can lead to unnecessary executions.
To avoid redundant executions and reduce resource usage, this change cancels any in-progress workflow for the same pull request when a new one is triggered by a commit push, ensuring only one active workflow per PR.

[TTOzzi]

If this change looks good, I think we could also consider applying the same setup to the pull_request workflow in swift-syntax.

[shahmishal]

We should look at adding this directly in the swiftlang/github-workflow repository.

[shahmishal]

However, it's ok to take this now in this repository.

[TTOzzi]

We should look at adding this directly in the swiftlang/github-workflow repository.

Yes, as you mentioned, it would be even better if we could apply this change across the board in swiftlang/github-workflows.
Since it's already applied to soundness (https://github.com/swiftlang/github-workflows/blob/main/.github/workflows/soundness.yml#L83-L86), I think we only need to apply it to swift_package_test.
Would it be okay if I open a PR to github-workflows for that?

[shahmishal]

Would it be okay if I open a PR to github-workflows for that?

Yes, that would be a great help. Thank you!

[TTOzzi]

I’ve opened a replacement PR in swiftlang/github-workflows, so I’m closing this one.
Thank you @shahmishal 🙇

[TTOzzi]

Sorry about that — I tried making changes over in swiftlang/github-workflows, but with the functionality currently provided by GitHub, it seems impossible to fully support all the places where swift_package_test is used.
So I've reopened this 😓

[bnbarham]

Happy to take this while we work out something for github-workflows regardless. Same for swift-syntax. Thanks @TTOzzi!