Settings → Rules → Rulesets → New ruleset → New branch ruleset
Ruleset Name：main
Enforcement status：Active
Target branches → Add target → Include default branch
Target branches → Add target → Include by pattern → Branch naming pattern：main
Branch rulesは以下にチェック
- Restrict deletions（デフォルトでチェック）
- Require a pull request before merging（チェックを追加）
- Block force pushes（デフォルトでチェック）
