I'm testing a gem in a Rails project.
The current Gemfile:
gem 'mygemname', path: '/path/to/my/gem'
If you use
bundle config local.GEM_NAME /path/to/local/git/repository from the command line then every time you reload your application it will load the latest source from your file system.
To remove the changes (when you have pushed your code to GitHub or RubyGems), you need to run
bundle config --delete local.GEM_NAME