convert: keep converted hg parents that are outside convert.hg.revs (BC) Before, when converting revisions without also including their already converted parents in convert.hg.revs, the parents would no longer be parents. That seems unfortunate and we dare to assume that nobody ever wants that. Instead, preserve parents that are outside the current convert range but already have been converted. The parents returned in getcommit() are unconditionally converted, so we introduce a separate optparents with optional parents.