.arcconfig

bookmarks: move the `mirror` option to the `paths` section

A new `bookmarks` section with a `mirror` option have been added. That option
has never been released yet.

This new options is limited since it affect all paths without distinction. In
case where a repository is interacting with multiple peers, being able to
control behavior on a path basis can be quite valuable.

In addition, having more variant of behavior would be interesting, especially a
mode where no bookmark exchanged is tried at all. Such new mode (implemented
later) make a lot of sense for configuration on a path-basis.

Configuration of the default behavior is still possible through the usage of
generic path configuration. The "old" config, becomes:

    [bookmarks]
    mirror=True

becomes:

    [path]
    *:bookmarks.mode=mirror

Differential Revision: https://phab.mercurial-scm.org/D11675

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