Babushka: dynamic removal of a dep requirement, based on a condition evaluated after previous requires have been processed

dynamic removal of a dep, based on a condition.rb

# dynamic removal of a dep requirement, 
#   based on a condition evaluated after previous requires have been processed

dep 'site' do
  requires \
    'system',
    'account',
    'site dir',
    'site options'
end

dep 'site options' do
  requires 'rvm user'
  setup {
    define_var :install_rvm,
      :message => "System ruby is \""+`ruby -v 2>&1`.chomp+"\" do you want to install your own in an RVM?",
      :choices => ['yes', 'no'],
      :default => 'no'
    ask_for_var :install_rvm.to_s
    definer.payload[:requires].delete 'rvm user' if var(:install_rvm)=='no'
  }
end

dep 'rvm user' do
  # ...
end