@Test
public void revisionId_should_return_different_sha1_after_commit() throws IOException, GitAPIException {

  Path projectDir = worktree.resolve("project");
  Files.createDirectory(projectDir);
  GitScmProvider provider = newGitScmProvider();
  String sha1before = provider.revisionId(projectDir);
  assertThat(sha1before).hasSize(40);
  createAndCommitFile("project/file1");
  String sha1after = provider.revisionId(projectDir);
  assertThat(sha1after).hasSize(40);
  assertThat(sha1after).isNotEqualTo(sha1before);
  assertThat(provider.revisionId(projectDir)).isEqualTo(sha1after);
}