git_gem

# File lib/rubygems/test_case.rb, line 411
  def git_gem name = 'a', version = 1
    have_git?

    directory = File.join 'git', name
    directory = File.expand_path directory

    git_spec = Gem::Specification.new name, version do |specification|
      yield specification if block_given?
    end

    FileUtils.mkdir_p directory

    gemspec = "#{name}.gemspec"

    open File.join(directory, gemspec), 'w' do |io|
      io.write git_spec.to_ruby
    end

    head = nil

    Dir.chdir directory do
      unless File.exist? '.git' then
        system @git, 'init', '--quiet'
        system @git, 'config', 'user.name',  'RubyGems Tests'
        system @git, 'config', 'user.email', 'rubygems@example'
      end

      system @git, 'add', gemspec
      system @git, 'commit', '-a', '-m', 'a non-empty commit message', '--quiet'
      head = Gem::Util.popen('git', 'rev-parse', 'master').strip
    end

    return name, git_spec.version, directory, head
  end