Having a Public Version Control system for your project is quite important, make it easy for people to find it. RubyGems makes it very easy.

Since the release of version 2 of RubyGems we can add any field to the metadata key.

In order to include the source_code_uri key add the following to the gempspec file of your project replacing the the URL with the one that matches your project.

  gem.metadata = {
    "source_code_uri" => "https://github.com/username/project",

Some people put the URL of their GitHub Repository in the gem.homepage fields. That's ok, but it would be prefereble to also put it in the source_code_uri field.