delta-find: assume the target-rev if not specified
This will be useful in the next patch, but I am putting it in its own commit to
make sure we can easily bisect any subtle side effect. (none are expected, but
still)
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"phabricator.uri": "https://phab.mercurial-scm.org/",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}