dirstate: deal with read-race for pure python code
If we cannot read the dirstate data, this is probably because a writing process
wrote it under our feet. So refresh the docket and try again a handful of time.
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"phabricator.uri": "https://phab.mercurial-scm.org/",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}