[develop] Actions rerun fixes.

[scottarnette]

Change Description

Fixed an issue regarding checkouts when rerunning a failed forked PR:

• Removed use of Actions checkout plugin for several reasons:
  • Version 1 of the plugin does not handle the race condition between the "merge commit" being created in Github and trying to checkout this commit.
  • Version 2 of the plugin addressed the above issue... but does not allow submodules to be checked out automatically.
  • We can use v2 of the plugin and manually checkout submodules... but v2 of the plugin does not checkout the full history of the repo, required for the submodule regression check.
  • Actions-based environment variables are set incorrectly on PR reruns of forked repositories...
• Replaced Actions plugin with our own checkout steps:
  • Clone the full repo.
  • Checkout the specific ref tied to the pull request number. We can do this because the workflow only runs on pull request events and reruns trigger a pull request event. Both cases contain the PR number.
  • Perform our own submodule checkout steps to grab the entire repository.
• Update submodule regression checker.
  • Checkout the specific ref tied to the pull request number when called from Actions.

See:
Actions | This Actions run builds a forked PR could be retried and checked out the codebase correctly.

Build 20766 | Buildkite run showing expected behavior with submodule regression check.

Consensus Changes

• Consensus Changes

API Changes

• API Changes

Documentation Additions

• Documentation Additions