backport.sh

#!/usr/bin/env bash

# Usage: ./backport.sh 'feature/im-play-nightly' 47bc4b2ade1baffbb6693ae149bca6126c2f352e 2.40 2.39 2.38 2.37

set -euo pipefail

if ! git diff --cached --exit-code; then
  echo "Nothing should be staged when running this script."
  exit 1
fi

if ! command -v git &> /dev/null; then
  echo "git could not be found."
  exit 1
fi

if ! command -v gh &> /dev/null; then
  echo "gh could not be found."
  exit 1
fi

if [[ -z "${1:-}" ]]; then
  echo "No base branch specified."
  exit 1
fi
base_branch="$1"

if [[ -z "${2:-}" ]]; then
  echo "No commit specified."
  exit 1
fi
commit="$2"

shift 2

if [[ -z "${*:-}" ]]; then
  echo "No backport branches specified."
  exit 1
fi

pr_id=$(gh pr list --search "$commit" --state merged --head "$base_branch" --json number --jq '.[0].number')
pr_url=$(gh pr view "$pr_id" --json url --jq '.url')
pr_title=$(gh pr view "$pr_id" --json title --jq '.title')
pr_reviewer=$(gh pr view "$pr_id" --json reviews --jq '.reviews | map(.author.login) | join(",")')

current_branch=$(git branch --show-current)

branches=("$@")
for branch in "${branches[@]}"; do
  git checkout "$branch"
  git pull origin "$branch"
  git checkout -b "${base_branch}_${branch}"
  git cherry-pick "$commit"
  git push origin "${base_branch}_${branch}"
  gh pr create --head "${base_branch}_${branch}" --base "$branch" --title "backport: $pr_title" --body "$pr_url" --reviewer "$pr_reviewer"
  # clean up
  git checkout "$current_branch"
  git branch -D "${base_branch}_${branch}"
done