install_into

# File lib/rubygems/request_set.rb, line 234
  def install_into dir, force = true, options = {}
    gem_home, ENV['GEM_HOME'] = ENV['GEM_HOME'], dir

    existing = force ? [] : specs_in(dir)
    existing.delete_if { |s| @always_install.include? s }

    dir = File.expand_path dir

    installed = []

    options[:development] = false
    options[:install_dir] = dir
    options[:only_install_dir] = true
    @prerelease = options[:prerelease]

    sorted_requests.each do |request|
      spec = request.spec

      if existing.find { |s| s.full_name == spec.full_name } then
        yield request, nil if block_given?
        next
      end

      spec.install options do |installer|
        yield request, installer if block_given?
      end

      installed << request
    end

    installed
  ensure
    ENV['GEM_HOME'] = gem_home
  end