.arcconfig

httppeer: expose capabilities for each command

This will help code using peers to sniff out exactly what servers
support.

Differential Revision: https://phab.mercurial-scm.org/D4436

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