clfilter: `bookmark.validdest` should run on unfiltered repo The logic recently added to `bookmark.validdest` uses data about obsolete changesets to see if a bookmark destination is valid. Obsolete changesets are likely to be filtered, so we need to work on an unfiltered repository.

clfilter: unfilter some parts of the push logic Computation of common changesets during push needs to be done on the widest set possible. An unfiltered version of the repo is kept for discovery and various revset calls. The discovery code itself enforces the filtering of unserved outgoing changeset.