How to use gems not in a Gemfile when working with bundler?

Question

When using bundler with a project in general and Rails specifically, you have access only to gems defined in your Gemfile. While this makes sense, it can be limiting. Mostly

Answer 1

Add to .gitignore

Gemfile.local
Gemfile.local.lock

Add to the project a Gemfile.local.sample file with the following content:

# Include gems that are note meant to be part of the project but for development purposes
# That's why Gemfile.local and Gemfile.local.lock must be git-ignored

# To use these gems:
#   1. Create a "Gemfile.local" file (at same level of "Gemfile")
#   2. Prepend "BUNDLE_GEMFILE=Gemfile.local" before "bundle install" or "bundle exec rails c" and so forth.

eval_gemfile "./Gemfile"

group :development, :test do
  # Suggested gems
  gem "awesome_print", require:"ap"
  gem "hirb"
  gem "pry"
  gem "pry-byebug"
  gem "pry-rails"
  gem "meta_request"

  # My gems
  gem "fivemat"
end