.arcconfig

hgweb: rewrite path generation for index entries

I think this code is easier to read. But the real reason to do this
is to eliminate a consumer of wsgirequest.

Differential Revision: https://phab.mercurial-scm.org/D2824

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