rollback: only restore dirstate and branch when appropriate. If the working dir parent was destroyed by rollback, then the old behaviour is perfectly reasonable: restore dirstate, branch, and bookmarks. That way the working dir moves back to an existing changeset rather than becoming an orphan. But if the working dir parent was unaffected -- say, you updated to an older changeset and then did rollback -- then it's silly to restore dirstate and branch. So don't do that. Leave the status of the working dir alone. (But always restore bookmarks, because that file refers to changeset IDs that may have been destroyed.)

rollback: refactor for readability; cosmetics. - clarify how we parse undo.desc - fix bad grammar in an error message - factor out ui local - rename some local variables - standardize string quoting