clear_cache.yml

# GitHub Caches are branch specific with non-default branches having access
# to the `default` branch.
# It appears that you cannot configure https://github.com/actions/cache to
# only cache if `default` branch.
# This workflow helps with housekeeping the caches.
# See https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows#force-deleting-cache-entries
name: Post-merge Cache Cleanup
on:
  pull_request:
    types:
      - closed

jobs:
  cleanup:
    runs-on: ubuntu-latest
    steps:
      - name: Cleanup
        run: |
          gh extension install actions/gh-actions-cache

          echo "Fetching list of cache key"
          cacheKeysForPR=$(gh actions-cache list -R $REPO -B $BRANCH -L 100 | cut -f 1 )

          ## Setting this to not fail the workflow while deleting cache keys.
          set +e
          echo "Deleting caches..."
          for cacheKey in $cacheKeysForPR
          do
              gh actions-cache delete $cacheKey -R $REPO -B $BRANCH --confirm
          done
          echo "Done"
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
          REPO: ${{ github.repository }}
          BRANCH: refs/pull/${{ github.event.pull_request.number }}/merge