Rails load additional gem without modify your project gemfile

how.md

bundler load gemfile by look up ENV["BUNDLE_GEMFILE"] , so your can set this enviromental variable to another gemfile , let say local_gemfile, and then in your local_gemfil, first load the project gemfile, and then add your additional ges.

# local_gemfile

 eval File.read('Gemfile')
 
 gem 'other_gems'