feat: support pruning merged preview branches

.github/workflows/prune_branches.yml

@@ -0,0 +1,32 @@
+name: Prune merged preview branches
+
+on:
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+
+  prune_branches:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+      pull-requests: write
+    steps:
+    - name: Checkout current repo
+      uses: actions/checkout@v3
+      with:
+        fetch-depth: 0
+    - name: Delete remote branches
+      run: |
+        BRANCHES=($(git branch -r | sed 's/^[[:space:]]*origin\///'))
+        if [ ${#BRANCHES[@]} -gt 0 ]; then
+          ./prune_preview_branches.sh "${BRANCHES[@]}"
+        else
+          echo "No branches to prune."
+        fi
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        DELETE_BRANCHES: "remote"

prune_preview_branches.sh

@@ -0,0 +1,70 @@
+#!/usr/bin/env bash
+
+set -e
+
+check_prerequisites() {
+  # Verify if jq is installed and GITHUB_TOKEN is set.
+  which jq &>/dev/null || (echo "Error: jq is required but not installed. You can download and install jq from <https://stedolan.github.io/jq/download/>." && exit 1)
+
+  test -n "$GITHUB_TOKEN" || (echo "Error: GITHUB_TOKEN (repo scope) is required but not set." && exit 1)
+}
+
+is_pr_merged() {
+  # Verify if a PR is merged.
+  local repo_owner="$1" repo_name="$2" pr_number="$3"
+  local api_url="https://api.github.com/repos/${repo_owner}/${repo_name}/pulls/${pr_number}"
+  local is_merged
+  is_merged=$(curl -fsSL -H "Authorization: token $GITHUB_TOKEN" "$api_url" | jq -r '.merged_at')
+  [[ -n "$is_merged" && "$is_merged" != "null" ]]
+}
+
+process_branch() {
+  # If the branch starts with 'preview', it checks if the associated pull request is merged.
+  # If it is merged, the branch is added to a list of branches to be pruned. Otherwise, the branch is skipped.
+  local branch="$1"
+  if [[ $branch == preview* ]]; then
+    IFS='/' read -r _ repo_owner repo_name pr_number <<< "$branch"
+    if is_pr_merged "$repo_owner" "$repo_name" "$pr_number"; then
+      echo "$branch: This preview PR is merged, will be pruned."
+      PRUNE_BRANCHES+=("$branch")
+    else
+      echo "$branch: This preview PR is not merged, skipping."
+    fi
+  fi
+}
+
+delete_branch() {
+  # Delete a branch based on the specified mode (local or remote).
+  local branch="$1" mode="$2"
+  echo "Deleting branch: $branch"
+  case "$mode" in
+    local)  git branch -D "$branch" ;;
+    remote) git push origin --delete "$branch" ;;
+    *)      echo "No action specified for branch deletion." ;;
+  esac
+}
+
+# Get the directory of this script.
+SCRIPT_DIR=$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" &>/dev/null && pwd)
+cd "$SCRIPT_DIR"
+
+check_prerequisites
+
+# Check if arguments are passed.
+if [ "$#" -eq 0 ]; then
+  set +o posix
+  mapfile -t BRANCHES < <(git branch --list | sed 's/^[*[:space:]]*//')
+else
+  BRANCHES=("$@")
+fi
+
+PRUNE_BRANCHES=()
+
+for branch in "${BRANCHES[@]}"; do
+  process_branch "$branch"
+done
+
+# Delete branches in the prune list.
+for branch in "${PRUNE_BRANCHES[@]}"; do
+  delete_branch "$branch" "${DELETE_BRANCHES:-}"
+done