.arcconfig

obsolete: add an explicit '_succs.copy()' method

Mimic the standard API for copying in the _succs class, it makes the code
slightly cleaner and will be needed later for copying markers at the same time
than copying the list content.

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