narrowcommands: drop unnecessary adding of '' for root directory It's now included by util.dirs(). Differential Revision: https://phab.mercurial-scm.org/D6405

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