コマンド

tomohiro@meos-MacBook-Pro p2091-training-rails % git branch --merged develop | grep -vE '^*|master$|develop$' | xargs -I % git branch -d %
Deleted branch feature/11-make_DB (was f649c37).
Deleted branch feature/15-docker (was 2e36c9f).
Deleted branch feature/22-fix_column (was 9c7b9e5).
Deleted branch feature/23-fix_time_zone (was 490c65b).
Deleted branch feature/24-fix_unnecessary_display (was bbe3dc1).
Deleted branch feature/25-change_css_to_scss (was 732ed9b).
Deleted branch feature/26-fix_assets_error (was 8eb92f8).
Deleted branch feature/27-change_Bootstrap3_to_4 (was dc48b81).
Deleted branch feature/28-fix_error_email (was 05921fd).
Deleted branch feature/29-fix_NoMethodError (was bc8e818).
Deleted branch feature/30-fix_instance_in_partical (was 58e7748).
Deleted branch feature/31-fix_logout_link (was 1dd66ab).
Deleted branch feature/34-fix_navigation_menu (was 1004767).
Deleted branch feature/35-create_register_form (was 02192e0).
Deleted branch feature/36-change_form_for_to_with (was 86b5e0f).
Deleted branch feature/37-Get_security_improved (was 9f1cd70).
Deleted branch feature/38-refactoring_if_statement (was b68524a).
Deleted branch feature/39-Refactoring_erb_to_slim (was 63b91b5).
Deleted branch feature/40-fix_setting_variable (was 2ed92e0).
Deleted branch feature/41-fix_sql (was 1c930b4).
Deleted branch feature/42-fix_sql (was ad4ce7d).
Deleted branch feature/43-solve_n+1 (was e9ad9fe).
Deleted branch feature/44-use_constant_using_config (was 6b9332c).
Deleted branch feature/45-add_validator (was 3e42e96).
Deleted branch feature/46-fix_select_box (was 76d21fc).
Deleted branch feature/47-add_animation_css (was a024ca5).
Deleted branch feature/48-fix_top_page_layout (was 22f00ed).
Deleted branch feature/49-Change_admin_settings_header_styles (was f6cfb3b).
Deleted branch feature/50-Display_items_according_to_category (was f6cfb3b).

削除した後のブランチ一覧

* develop
  feature/32-add_dummy_data
  feature/33-add_Enumerize
  master

参考記事

https://gist.github.com/miukoba/fc3c10a25c1c675c1e97