rebase: track new nodes when --keep is set
When --keep is passed with rebase, the new nodes created are not
accessible from templates.
This change enables accessing the newly-created nodes from nodechanges,
just as if --keep was not set.
Differential Revision: https://phab.mercurial-scm.org/D6880
{
"conduit_uri": "https://phab.mercurial-scm.org/api",
"repository.callsign": "HG",
"arc.land.onto.default": "@",
"base": "hg:.^"
}