試しにGithubからrails-masterをダウンロードして、rbファイルの行数をカウントしてみました。
wc -l `find rails-master/ -name '*.rb'`
結果
(中略)
233 rails-master//railties/test/paths_test.rb
75 rails-master//railties/test/rack_logger_test.rb
56 rails-master//railties/test/rails_info_controller_test.rb
92 rails-master//railties/test/rails_info_test.rb
1244 rails-master//railties/test/railties/engine_test.rb
126 rails-master//railties/test/railties/generators_test.rb
278 rails-master//railties/test/railties/mounted_engine_test.rb
200 rails-master//railties/test/railties/railtie_test.rb
60 rails-master//railties/test/test_info_test.rb
128 rails-master//tasks/release.rb
10 rails-master//version.rb
240824 total
wcコマンドは -lオプションで行数をカウントします。