dagop: add smartset interface to filectxancestors()
The original filectx API is kept public since we'll need it to walk ancestor
(rev, match) pairs efficiently. The current implementation scans ancestors
twice for 'hg log -fp FILE'.
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}