clone: fix updaterev to update to latest branch changeset (issue4528) Before this patch if clone --updaterev points to branch which head on src repo wasnt in dest repo, clone updated dest repo to default branch. After applying this patch, if changeset from src repo pointing at given branch is not in dest repo, it searches for changeset pointing for given branch locally in dest repo. Lookup in destination repo: 559: uprev = destrepo.lookup(update) is wrapped by try/except block to preserve current behaviour when given revset to -u is not found - it will not fail,but silently update dest repo to head of default branch.