typing: add a few type hints to `mercurial/revlog.py`
Somewhere between hg
3dbc7b1ecaba and hg
8e3f6b5bf720, pytype stopped being able
to infer the type for `_docket_file` and `compress()`. Lock those types in
before they get lost.
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"phabricator.uri": "https://phab.mercurial-scm.org/",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}