Gem::Request#user_agent

# File tmp/rubies/ruby-3.1.3/lib/rubygems/request.rb, line 272
def user_agent
  ua = "RubyGems/#{Gem::VERSION} #{Gem::Platform.local}".dup

  ruby_version = RUBY_VERSION
  ruby_version += "dev" if RUBY_PATCHLEVEL == -1

  ua << " Ruby/#{ruby_version} (#{RUBY_RELEASE_DATE}"
  if RUBY_PATCHLEVEL >= 0
    ua << " patchlevel #{RUBY_PATCHLEVEL}"
  elsif defined?(RUBY_REVISION)
    ua << " revision #{RUBY_REVISION}"
  end
  ua << ")"

  ua << " #{RUBY_ENGINE}" if RUBY_ENGINE != "ruby"

  ua
end