dagop: don't import nullrev from .node twice
See 59fa3890d40a.
Differential Revision: https://phab.mercurial-scm.org/D12120
--- a/mercurial/dagop.py Thu Jan 27 22:24:11 2022 +0100
+++ b/mercurial/dagop.py Mon Jan 31 18:04:11 2022 +0300
@@ -9,7 +9,6 @@
import heapq
-from .node import nullrev
from .thirdparty import attr
from .node import nullrev
from . import (