Artifact does not get added to `.gitignore` on failed multi-add

[pared]

Following test passes:

def test_add_multiple_with_exception(tmp_dir, scm, dvc, mocker):
    tmp_dir.gen({"file": "file content", "other": "other file content"})
    original_move = dvc.cache.local.tree.move

    def raise_move(from_info, to_info, mode=None):
        if str(from_info) == "other":
            raise Exception
        else:
            original_move(from_info, to_info, mode)

    assert not (tmp_dir / ".gitignore").exists()
    mocker.patch.object(dvc.cache.local.tree, "move", side_effect=raise_move)
    try:
        dvc.add(["file", "other"])
    except:
        pass
    assert (tmp_dir / "file.dvc").exists()
    assert (tmp_dir / ".gitignore").exists()
    assert (tmp_dir / ".gitignore").read_text() == ''

How it should be?
.gitignore should contain file even though the whole add command failed. As of now, we end up successfully adding file to dvc but it is not ignored. At least we should be informed about potential problems.