revlog: list older-but-still-around file in `files`
These older files will eventually be removed, but we have to take them in account until they are. So we update `files` to keep fncache happy.
Differential Revision: https://phab.mercurial-scm.org/D10868
from typing import Optional
version: int
def b85encode(text: bytes, pad: Optional[int]) -> bytes: ...
def b85decode(text: bytes) -> bytes: ...