# File lib/bundler/dsl.rb, line 164
    def github(repo, options = {})
      raise ArgumentError, "Github sources require a block" unless block_given?
      github_uri  = @git_sources["github"].call(repo)
      git_options = normalize_hash(options).merge("uri" => github_uri)
      git_source  = @sources.add_git_source(git_options)
      with_source(git_source) { yield }
    end