Gem::LocalRemoteOptions#add_source_option

# File tmp/rubies/ruby-4.0.0/lib/rubygems/local_remote_options.rb, line 101
def add_source_option
  accept_uri_http

  add_option(:"Local/Remote", "-s", "--source URL", Gem::URI::HTTP,
             "Append URL to list of remote gem sources") do |source, options|
    source << "/" unless source.end_with?("/")

    if options.delete :sources_cleared
      Gem.sources = [source]
    else
      Gem.sources << source unless Gem.sources.include?(source)
    end
  end
end