copies-rust: make the comparison aware of the revision being current merged
This make no significant performance change in practice (all ±2%) in practice,
but it will help us to distinct between some semantically different cases later
on.
Differential Revision: https://phab.mercurial-scm.org/D9498
from typing import Optional
version: int
def b85encode(text: bytes, pad: Optional[int]) -> bytes: ...
def b85decode(text: bytes) -> bytes: ...