.arcconfig

commands: use the new API to access hidden changesets in various commands

In previous patches, we have added an internal API to unhide hidden changesets.
This patch makes the following command use that api in nowarn mode i.e. there
will be no warning while accessing hidden changesets.

cat, diff, export, files, heads, identify, log, manifest, parents, status

This patch also adds test demonstarting the behaviour.

.. feature:: Accessing hidden changesets

    Set config option 'experimental.directaccess = True' to access hidden
    changesets from read only commands.

Differential Revision: https://phab.mercurial-scm.org/D1735

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