.arcconfig

cmdutil: make node parameter of makefileobj() mandatory (API)

(repo, node) pair will be replaced with ctx, so makefilename() can be easily
ported to templater.

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