class Gem::Commands::UpdateCommand

def highest_installed_gems # :nodoc:
  hig = {} # highest installed gems
  # Get only gem specifications installed as --user-install
  Gem::Specification.dirs = Gem.user_dir if options[:user_install]
  Gem::Specification.each do |spec|
    if hig[spec.name].nil? || hig[spec.name].version < spec.version
      hig[spec.name] = spec
    end
  end
  hig
end