class Bundler::Runtime

def setup(*groups)
  groups.map! { |g| g.to_sym }
  # Has to happen first
  clean_load_path
  specs = groups.any? ? @definition.specs_for(groups) : requested_specs
  setup_environment
  Bundler.rubygems.replace_entrypoints(specs)
  # Activate the specs
  specs.each do |spec|
    unless spec.loaded_from
      raise GemNotFound, "#{spec.full_name} is missing. Run `bundle` to get it."
    end
    if activated_spec = Bundler.rubygems.loaded_specs(spec.name) and activated_spec.version != spec.version
      e = Gem::LoadError.new "You have already activated #{activated_spec.name} #{activated_spec.version}, " \
                             "but your Gemfile requires #{spec.name} #{spec.version}. Prepending " \
                             "`bundle exec` to your command may solve this."
      e.name = spec.name
      if e.respond_to?(:requirement=)
        e.requirement = Gem::Requirement.new(spec.version.to_s)
      else
        e.version_requirement = Gem::Requirement.new(spec.version.to_s)
      end
      raise e
    end
    Bundler.rubygems.mark_loaded(spec)
    load_paths = spec.load_paths.reject {|path| $LOAD_PATH.include?(path)}
    $LOAD_PATH.unshift(*load_paths)
  end
  setup_manpath
  lock
  self
end