subrepo: don't attempt to share remote sources (issue5793) Untangling _abssource() to resolve the new subrepo relative to the shared parent's share path, and then either sharing from there (if it exists), or cloning to that location and then sharing, is probably more than should be attempted on stable. Absolute subrepo references are discouraged, so for now, this resumes the behavior prior to 68e0bcb90357 of cloning the absolute subrepo locally.