.arcconfig

wireprotoserver: py3 helpfully calls adds HTTP_ to CONTENT_LENGTH

Just handle both with a membership check, preferring the HTTP_
namespaced version. Sigh.

Differential Revision: https://phab.mercurial-scm.org/D2310

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