.arcconfig

diff: invoke the file prefetch hook

By invoking it this deep within the command, we pick up both subrepo and hgweb
support, as well as --patch support for commands that implement logopts.

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