Deleting stale Paperclip attachment styles from the server

Copy# Config #######################################################################
delete_styles = [:gallery, :thumbnail, :whatever]
scope = YourModel # A scope on the class with #has_attached_file
attachment_name = :image # First argument of #has_attached_file
noop = false # Use this to dry-run

# Script #######################################################################
scope.find_in_batches(:batch_size => 100) do |records|
  records.map(&attachment_name).each do |attachment|
    paths = delete_styles.map do |style|
      raise 'Refuse to delete original' if style == :original
      attachment.path(style)
    end

    existing_paths = paths.select(&File.method(:file?))
    existing_paths.each do |path|
      parent_dir = File.dirname(path)

      puts "Deleting #{path}"
      FileUtils.rm path unless noop

      puts "Deleting empty parent directory #{parent_dir}"
      # rmdir will only ever delete an empty directory
      FileUtils.rmdir parent_dir unless noop

      puts
    end
  end
end