Gem::Commands::UpdateCommand#which_to_update

# File tmp/rubies/ruby-3.0.5/lib/rubygems/commands/update_command.rb, line 304
def which_to_update(highest_installed_gems, gem_names, system = false)
  result = []

  highest_installed_gems.each do |l_name, l_spec|
    next if not gem_names.empty? and
            gem_names.none? {|name| name == l_spec.name }

    highest_remote_tup = highest_remote_name_tuple l_spec
    highest_remote_ver = highest_remote_tup.version
    highest_installed_ver = l_spec.version

    if system or (highest_installed_ver < highest_remote_ver)
      result << Gem::NameTuple.new(l_spec.name, [highest_installed_ver, highest_remote_ver].max, highest_remote_tup.platform)
    end
  end

  result
end