.arcconfig

dirstate: use `add` in the deprecation message about `add`

The previous message was talking about `remove`.

Differential Revision: https://phab.mercurial-scm.org/D11224

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