.arcconfig

branchmap: rename partial -> bcache

The name better reflects that we have a branchcache object here, even if at
*some point* it is still being constructed.

Differential Revision: https://phab.mercurial-scm.org/D5290

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