How to use a local gem in your Gemfile
You can use local copies of gems in your
Gemfile like this:
gem 'spreewald', :path => '~/gems/spreewald'
As soon as you have bundled your project with the local copy of the gem, all code changes in the copy will be available on your project. So you can for example set a debugger (or add console output) in the gem and use it from your project.
If you checked out the gem using git (or any other versioning tool), you can easily reset your changes afterwards or make a pull request for the gem if you improved it.
You can also install the gem locally and override the version from git:
cd ~/gems/spreewald rvm use 2.5.1 # or rbenv local 2.5.1 rake install # use gem uninstall geordi and gem install geordi to install the remove version again