gistfile1.rb

User.current = User.find_by_login "admin"
old_name = "Puppet Master"
new_name = "common"

params = Hostgroup.find_by_name(old_name).group_parameters
old_params = params.collect{|p| [p.name, p.value]}

new_group = Hostgroup.find_by_name(new_name)
old_params.each do |param|
  new_group.group_parameters << GroupParameter.create(:name => param[0], :value => param[1])
end