.arcconfig

revlog: add attribute on revlogs that specifies its kind

The sidedata logic needs to check whether the revlog it's working on is a
changelog, a manifest or a filelog.
Furthermore, future versions of the revlog format will most likely see a split
between the three types (i.e. they will store different information), so having
this will be useful for other future endeavors as well.

Differential Revision: https://phab.mercurial-scm.org/D10151

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