def test_get_valid_ref_without_origin(self):
        """Test that _get_valid_ref falls back to empty tree ref when there's no origin."""
        # Create a new directory with a git repo but no origin
        no_origin_dir = os.path.join(self.test_dir, 'no-origin')
        os.makedirs(no_origin_dir, exist_ok=True)

        # Initialize git repo without origin
        self._execute_command('git --no-pager init', no_origin_dir)
        self._execute_command(
            "git --no-pager config user.email 'test@example.com'", no_origin_dir
        )
        self._execute_command(
            "git --no-pager config user.name 'Test User'", no_origin_dir
        )

        # Create a file and commit it
        with open(os.path.join(no_origin_dir, 'file1.txt'), 'w') as f:
            f.write('Content in repo without origin')
        self._execute_command('git --no-pager add file1.txt', no_origin_dir)
        self._execute_command(
            "git --no-pager commit -m 'Initial commit'", no_origin_dir
        )

        # Create a custom GitHandler with a modified _get_default_branch method for this test
        class TestGitHandler(GitHandler):
            def _get_default_branch(self) -> str:
                # Override to handle repos without origin
                try:
                    return super()._get_default_branch()
                except IndexError:
                    return 'main'  # Default fallback

        # Create a new GitHandler for this repo
        no_origin_handler = TestGitHandler(self._execute_command)
        no_origin_handler.set_cwd(no_origin_dir)

        # Clear the executed commands to start fresh
        self.executed_commands = []

        ref = no_origin_handler._get_valid_ref()

        # Verify that git commands were executed
        self.assertTrue(
            any(
                cmd.startswith('git --no-pager rev-parse --verify')
                for cmd, _ in self.executed_commands
            )
        )

        # Should have fallen back to the empty tree ref
        self.assertEqual(
            ref,
            '$(git --no-pager rev-parse --verify 4b825dc642cb6eb9a060e54bf8d69288fbee4904)',
        )

        # Verify the ref exists (the empty tree ref always exists)
        result = self._execute_command(
            'git --no-pager rev-parse --verify 4b825dc642cb6eb9a060e54bf8d69288fbee4904',
            no_origin_dir,
        )
        self.assertEqual(result.exit_code, 0)
Test that _get_valid_ref falls back to empty tree ref when there's no origin.
tests/unit/test_git_handler.py