code: def test_get_diff_command_error(mock_repo):
      # given
      mock_repo.git.diff.side_effect = git.GitCommandError("diff")
  
      # when
      diff = get_diff(mock_repo, "some_ref")
  
      # then
      mock_repo.git.diff.assert_called_once_with(
          "some_ref", index=False
      )
      assert diff is None
  
imports: import datetime
  import git
  from git import Repo
  from mock import MagicMock, patch
  from neptune.internal.utils.git import GitInfo, get_diff, get_relevant_upstream_commit, get_repo_from_git_ref, get_uncommitted_changes, get_upstream_index_sha, search_for_most_recent_ancestor, to_git_info, track_uncommitted_changes
  from neptune.types import GitRef
label_desc: Use image node_id 4 for calling a global function with example usage: test_get_diff_command_error(mock_repo) without return types