.arcconfig

blackbox: extract logger class from ui wrapper

This moves most functions to new blackboxlogger class. The ui wrapper will
be removed later.

{
    "conduit_uri": "https://phab.mercurial-scm.org/api",
    "repository.callsign": "HG",
    "arc.land.onto.default": "@",
    "base": "hg:.^"
}