Gem::BundlerVersionFinder.bundle_update_bundler_version

# File tmp/rubies/ruby-3.4.1/lib/rubygems/bundler_version_finder.rb, line 23
def self.bundle_update_bundler_version
  return unless ["bundle", "bundler"].include? File.basename($0)
  return unless "update".start_with?(ARGV.first || " ")
  bundler_version = nil
  update_index = nil
  ARGV.each_with_index do |a, i|
    if update_index && update_index.succ == i && a =~ Gem::Version::ANCHORED_VERSION_PATTERN
      bundler_version = a
    end
    next unless a =~ /\A--bundler(?:[= ](#{Gem::Version::VERSION_PATTERN}))?\z/
    bundler_version = $1 || true
    update_index = i
  end
  bundler_version
end