ruby - 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 I find it limiting when I want to use a certain RSpec formatter that the rest of the team doesn't use. Unless it's in the Gemfile, it isn't accessible.

Any way around it or I have to add it to Gemfile?

Update: my problem wasn't Bundler but Spork. When running RSpec without Spork I had no problem of using whatever formatter I wanted.

Update #2: it looks like that using Bundler is still the cause of the problem. The difference between using Spork and not using Spork, is that when running RSpec without Spork, it loads the formatter before loading your project and getting into the Bundler "sandbox".

With Bundler:

$ bundle exec irb
>> require 'fivemat'
LoadError: cannot load such file -- fivemat

from (irb):1:in `require'
from (irb):1
from /Users/arikfr/.rvm/rubies/ruby-1.9.3-p194/bin/irb:16:in `<main>'

Without Bundler:

$ irb
>> require 'fivemat'
=> true

Answer 1

In ChiliProject we allow users to create a Gemfile.local which is included into the main Gemfile on load. This allows users to specify additional gems without having to change our Gemfile to ease updates.

For that, we have included the following code at the bottom of our Gemfile.

gemfile_local = File.expand_path('Gemfile.local', __dir__)
if File.readable?(gemfile_local)
  puts "Loading #{gemfile_local}..." if $DEBUG
  instance_eval(File.read(gemfile_local))
end

The Gemfile.local itself is excluded from the repository via .gitignore.