.arcconfig

rhg: small refactor: stop using a magical constant "+ 1"

Instead, directly do what the "+ 1" was supposed to achive:
call hash_encode.

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