.arcconfig

merge: invoke scmutil.fileprefetchhooks() prior to applying updates

This moves the file list calculation into core, so other extensions don't need
to duplicate it.

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