branchcache: do not accept "empty update" This currently does not happens and it will be simpler that is remains that way. If all update do something, we will be able to simply declare, in a later changesets, that all update to result in a dirty branchcache.

branchcache: avoid created a `None` filter repoview when writing The repoview class is not intended to be used for unfiltered repository.

stream-clone-tests: stop filtering non existent warning This filtering was introduced in 74c004a515bc, however there is already no warning in that changeset. So I guess the warnings existed when we the patch was created but the problem was solved in another changeset that 74c004a515bc, rebased on.