destroyed: filter unknown before computing branchcache Branchcache of filtered version need up to date phase data.

branchmap: disable fallback to unfiltered branchcache Disables this simple optimisation to allow coming more powerfull approach: cache collaboration. Our goal is to have branchcache collaborate. This means that unfiltered branchcache will fallback to some filtered branchcache if invalid. We can't have the filtered branchcache to use the unfiltered one. That would loop.

localrepo: filter unknown nodes from the phasecache on destroyed When commit is followed by strip (qrefresh), phasecache contains nodes that were removed from the changelog. Since phasecache is filecached with .hg/store/phaseroots which doesn't change as a result of stripping, we have to filter it manually. If we don't write it immediately, the next time it is read from disk the nodes will be filtered again. That's what happened before, but there's no reason not to write it immediately. The change in test-keyword.t is caused by the above.

phases: make _filterunknown a member function of phasecache We'd like the ability to call filterunknown on an existing phasecache instance after nodes are destroyed.

localrepo: drop `_cacheabletip` method It iss dead code now.

branchmap: drop `_cacheabletip` usage in `updatecache` Nobody overwrite the `_cacheabletip` any more. We always update the cache for the whole repo and write it to disk (or at list try to). The `updatecache` code is simplied to remove the double phase logic associated with _cacheabletip.

mq: drop `_cacheabletip` usage Strip have dedicated work around to solve the same problem, strip is even a fraction faster without that thanks to simpler update process of the branchcache.

bundlerepo: drop use of `_cacheabletip` Now that bundlerepo use a read only VFS, we do not worry about what part of the branchmap is written back to disk. Nothing is written at all.

bundlerepo: enforce reading from core repo only We do not want anything computed with the bundle overlay to be written back in the repo. Such write will likely contains invalid data. The short terms goal of this change is to drop use of `_cacheabletip` in bundle repo.

branchmap: ignore Abort error while writing cache Read only vfs can now raise Abort exception. Note that encoding.local are also a possible raiser.