Delete merge release branches (#15262)

* delete branches when closing previous automatically created PRs

* link closed PRs in the new PR

.github/workflows/create-merge-release-into-dev-pr.yml

@@ -79,10 +79,18 @@ jobs:
               echo "Successfully merged $RELEASE_BRANCH into $BASE_BRANCH and pushed"
             else
               # Close all previous PRs with label
-              for pr_number in $(gh pr list --label create-merge-release-into-dev-pr --json number --jq='.[].number'); do
-                gh pr close "$pr_number"
+              pr_numbers=$(gh pr list --label create-merge-release-into-dev-pr --json number --jq='.[].number')
+              for pr_number in $pr_numbers; do
+                gh pr close "$pr_number" --delete-branch
               done
 
+              pr_body=$(
+                echo 'Created by GitHub action'
+                for pr_number in $pr_numbers; do
+                  echo "Replaces #$pr_number"
+                done
+              )
+
               TEMP_BRANCH="merge-$RELEASE_BRANCH-$(date "+%Y%m%d%H%M%S")"
 
               git branch "$TEMP_BRANCH" "$RELEASE_BRANCH"
@@ -93,7 +101,7 @@ jobs:
                 --base "$BASE_BRANCH" \
                 --head "$TEMP_BRANCH" \
                 --title "Merge $RELEASE_BRANCH into $BASE_BRANCH" \
-                --body 'Created by GitHub action' \
+                --body "$pr_body" \
                 --label create-merge-release-into-dev-pr
               echo "Created a PR to merge $RELEASE_BRANCH ($TEMP_BRANCH) into $BASE_BRANCH"
             fi