add_always_install

# File lib/rubygems/resolver/installer_set.rb, line 53
  def add_always_install(dependency)
    request = Gem::Resolver::DependencyRequest.new dependency, nil

    found = find_all request

    found.delete_if { |s|
      s.version.prerelease? and not s.local?
    } unless dependency.prerelease?

    found = found.select do |s|
      Gem::Source::SpecificFile === s.source or
        Gem::Platform::RUBY == s.platform or
        Gem::Platform.local === s.platform
    end

    if found.empty?
      exc = Gem::UnsatisfiableDependencyError.new request
      exc.errors = errors

      raise exc
    end

    newest = found.max_by do |s|
      [s.version, s.platform == Gem::Platform::RUBY ? -1 : 1]
    end

    @always_install << newest.spec
  end