revlog: reset _nodepos after strip When using the pure revlog parser, _nodepos is used to keep track of the position during index scanning in the non-cached cache. If it is out of bounds, BaseIndexObject._fix_index will assert. Since strip can actually remove the position scanned last, make sure to reset it. Add an assertion in the place where the invariance is clearer. Differential Revision: https://phab.mercurial-scm.org/D3188