monkey patch to Ancestry to add tree cloning

clone_with_modifications.rb

module Ancestry
  # https://github.com/stefankroes/ancestry
  
  module InstanceMethods
    # Clone an object and all children
    # => replacing values with those from attributes if present
    # => setting parent to new parent if present
    # => setting the "original_id_field_name" if present to the id of the original object
    #
    # Example use_case:
    #
    #   class Category < ActiveRecord::Base
    #     belongs_to :project
    #     belongs_to :source_category, :class_name => "Category"
    #     scope :defaults, where(:project_id => nil)
    #     def self.import_from_defaults_for(project)
    #       defaults.roots.all.each do |root|
    #       root.clone_with_modifications!({:project_id => project.id}, nil, :source_category_id)
    #     end
    #   end
    #   
    #   class Project < ActiveRecord::Base
    #     has_many :categories, :dependent => :destroy
    #     after_create Proc.new { |p| Category.import_from_defaults_for(self) }
    #   end
    #
    def clone_with_modifications!(attributes = nil, parent = nil, original_id_field_name = nil)
      clone = self.class.create!(self.attributes.merge(:ancestry => nil).merge(attributes))
      clone.send("#{original_id_field_name}=", self.id) if original_id_field_name
      clone.parent = parent
      self.children.each { |child| child.clone_with_modifications!(attributes, clone, original_id_field_name) }
      clone.save!
    end
  end
end