rhg: don't run `blackbox` if not activated
You currently have no way of turning off blackbox. Aside from being a bug, this
can be annoying if you use `rhg` in your shell prompt, but also because the
current implementation of blackbox is quite slow due to `user` querying.
Differential Revision: https://phab.mercurial-scm.org/D11813
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"phabricator.uri": "https://phab.mercurial-scm.org/",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}