trustieforge/app/models/attachment_history.rb

class AttachmentHistory < ActiveRecord::Base
  belongs_to :attachment,foreign_key: 'attachment_id'
  cattr_accessor :storage_history_path
  @@storage_history_path = Redmine::Configuration['attachments_storage_path'] || File.join(Rails.root, "files")

  # Returns file's location on disk
  def diskfile_history
    File.join(self.class.storage_history_path, disk_directory.to_s, disk_filename.to_s)
  end

  def increment_download
    increment!(:downloads)
  end
end