Cleanup Github Actions cache for pull requests

Author: dolfinus

.github/workflows/cache-cleanup.yml

@@ -0,0 +1,41 @@
+name: Cleanup caches after merge
+on:
+    pull_request:
+        types:
+            - closed
+    workflow_dispatch:
+
+jobs:
+    cleanup:
+        runs-on: ubuntu-latest
+
+        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
+            contents: read
+
+        steps:
+            - name: Check out code
+              uses: actions/checkout@v4
+
+            - name: Cleanup cache
+              run: |
+                  gh extension install actions/gh-actions-cache
+
+                  REPO=${{ github.repository }}
+                  BRANCH=refs/pull/${{ github.event.pull_request.number }}/merge
+
+                  echo "Fetching list of cache key"
+                  cacheKeysForPR=$(gh actions-cache list -R $REPO -B $BRANCH --limit 100 --sort size | 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 }}