如果您使用的是捆绑器，您需要在Gemfile中添加如下内容：

In case you are using bundler, you need to add something like this to your Gemfile:

gem 'redcarpet', :git => 'git://github.com/tanoku/redcarpet.git'

和的情况下，有 .gemspec 文件，它应该能够在运行 bundle install 时获取并安装gem。

And in case there is .gemspec file, it should be able to fetch and install the gem when running bundle install.