Add `default` DSL to placeholder https://github.com/jnicklas/turnip/pull/173

placeholder.rb

placeholder :user_name do
  match /admin: (.*)/ do |user_name|
    User.find_by!(name: user_name, role: :admin)
  end

  default do |user_name|
    User.find_by!(name: user_name)
  end
end

defaultという名前にするなら順番が逆でも動いて欲しい感じがありますね

placeholder :user_name do
  default do |user_name|
    User.find_by!(name: user_name, role: :normal)
  end

  match /admin/ do |user_name|
    User.find_by!(name: 'admin', role: :admin)
  end
end