cleanup-after-merge.yml

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name: Cleanup after merge

on:
  pull_request:
    types:
      - closed

permissions:
  # `actions:write` permission is required to delete caches
  #   See also: https://docs.github.com/en/rest/actions/cache?apiVersion=2022-11-28#delete-a-github-actions-cache-for-a-repository-using-a-cache-id
  actions: write

jobs:
  delete:
    name: Cleanup
    runs-on: ubuntu-latest

    steps:
      - name: Delete github caches belonging to branch {{ github.ref }}
        env:
          GH_TOKEN: ${{ github.token }}
        run: |
          gh extension install actions/gh-actions-cache
          
          repo="${{ github.repository }}"
          branch="${{ github.ref }}"
          
          printf "Fetching list of cache keys for branch %s..." "${branch}"
          cache_keys_for_pr=( $( \
            gh actions-cache \
              --repo "${repo}" \
              --branch "${branch}" \
              list \
              | cut -f 1) \
          )
          echo " Done."
          
          # Setting this to not fail the workflow while deleting cache keys. 
          set +e
          if [[ -n "${cache_keys_for_pr[*]}" ]]
          then
            echo "Found the following cache keys:"
            for cache_key in "${cache_keys_for_pr[@]}"
            do
              echo "  ${cache_key}"
            done
            echo "Starting deletion of caches"
            for cache_key in "${cache_keys_for_pr[@]}"
            do
              printf "  Deleting cache with key %s..." "${cache_key}"
              gh actions-cache delete \
                --repo "${repo}" \
                --branch "${branch}" \
                --confirm \
                "${cache_key}" \
                1> /dev/null
              echo " Done."
            done
            echo "All caches deleted."
          else
            echo "No caches on branch ${branch} found. Nothing to delete."
          fi