How to install gem from GitHub source

You just add the following line to your local ~/.gemrc file (it is in your home folder):

gem: --no-document

or you can add this line to the global gemrc config file.

Here is how to find it (in Linux):

strace gem source 2>&1 | grep gemrc

The --no-document option is documented in the RubyGems CLI Reference.

You don't need to build the gem locally. In your gemfile you can specify a github source with a ref, branch or tag.

gem 'rails', git: 'git://github.com/rails/rails.git', ref: '4aded'
gem 'rails', git: 'git://github.com/rails/rails.git', branch: '2-3-stable'
gem 'rails', git: 'git://github.com/rails/rails.git', tag: 'v2.3.5'

Then you run bundle install or the short form is just bundle.

Read more about it here: http://bundler.io/man/gemfile.5.html#GIT

Update: There's a github source identifier.

gem 'country_select', github: 'stefanpenner/country_select'

However, they warn against using it: NOTE: This shorthand should be avoided until Bundler 2.0, since it currently expands to an insecure git:// URL. This allows a man-in-the-middle attacker to compromise your system.

After Bundler 2.0, you can get around the above issue with this statement near the top of the Gemfile:

git_source(:github) { |repo| "https://github.com/#{repo}.git" }