docs: def git_handler(unused_build_context, target, fetch, package_dir, tar):
      """Handle remote Git repository URI.
  
      Clone the repository under the private builder workspace (unless already
      cloned), and add it to the package tar (filtering out git internals).
  
      TODO(itamar): Support branches / tags / specific commit hashes
      TODO(itamar): Support updating a cloned repository
      TODO(itamar): Handle submodules?
      TODO(itamar): Handle force pulls?
      """
      target_name = split_name(target.name)
      # clone the repository under a private builder workspace
      repo_dir = join(package_dir, fetch.name) if fetch.name else package_dir
      try:
          repo = git.Repo(repo_dir)
      except (InvalidGitRepositoryError, NoSuchPathError):
          repo = git.Repo.clone_from(fetch.uri, repo_dir)
      assert repo.working_tree_dir == repo_dir
      tar.add(package_dir, arcname=target_name, filter=gitfilter)