path: keep the path instance in the `pulloperation` This will allow more pull code to use the path options. Ideally we would modify the peer API to keep the path instance. However that is much more churn that I can deal with for my current goal: adjusting a user facing API for a new feature before we release it in the 6.0 changesets. So I am taking a shortcut that seems reasonable. Differential Revision: https://phab.mercurial-scm.org/D11674