dirstate: fix a potential traceback when in `copy` and `rename`
Before this changes, calling `hg copy` or `hg rename` could trigger a traceback
about using an invalidated dirstate. This wasn't caught by the test as it needed
the blackbox extension to preload the dirstate first in a way "refresh"
invalidates it.
Changing the context creation patterns fixes it.
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"phabricator.uri": "https://phab.mercurial-scm.org/",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}