templater: load template fragments from [templates] section in map file This allows us to %include map-cmdline.<style> file in our .hgrc files. The syntax is slightly different as hgrc doesn't support loading an external template file, but map-cmdline files don't use this feature, so the syntax can be considered identical in practice. Unnamed section is remapped for backward compatibility.

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