class Gem::Commands::CleanupCommand

def get_gems_to_cleanup
  gems_to_cleanup = @candidate_gems.select do |spec|
    @primary_gems[spec.name].version != spec.version
  end
  default_gems, gems_to_cleanup = gems_to_cleanup.partition(&:default_gem?)
  uninstall_from = options[:user_install] ? Gem.user_dir : Gem.dir
  gems_to_cleanup = gems_to_cleanup.select do |spec|
    spec.base_dir == uninstall_from
  end
  @default_gems += default_gems
  @default_gems.uniq!
  @gems_to_cleanup = gems_to_cleanup.uniq
end