@Test
  public void showNotebookHistory() throws GitAPIException, IOException {
    // given
    notebookRepo = new GitNotebookRepo(conf);
    assertThat(notebookRepo.list()).isNotEmpty();

    // when
    List<Rev> testNotebookHistory = notebookRepo.history(TEST_NOTE_ID);

    // then
    assertThat(testNotebookHistory).isNotEmpty();
  }
  @Test
  public void initNonemptyNotebookDir() throws IOException, GitAPIException {
    // given - .git does not exit
    File dotGit = new File(Joiner.on(File.separator).join(notebooksDir, ".git"));
    assertThat(dotGit.exists()).isEqualTo(false);

    // when
    notebookRepo = new GitNotebookRepo(conf);

    // then
    Git git = notebookRepo.getGit();
    assertThat(git).isNotNull();

    assertThat(dotGit.exists()).isEqualTo(true);
    assertThat(notebookRepo.list()).isNotEmpty();

    List<DiffEntry> diff = git.diff().call();
    assertThat(diff).isEmpty();
  }