unstable: use the `_mutablerevs` function when computing content divergent
This is a useful function to get the revision relevant to these computation,
lets make sure all code use it, so that we can improve that `_mutablerevs`
function in a later changeset.
from typing import Optional
version: int
def b85encode(text: bytes, pad: Optional[int]) -> bytes: ...
def b85decode(text: bytes) -> bytes: ...