branchcache: change the _delayed flag to an explicit `_dirty` flag This is more consistent with the logic we use for other object and it open the way to a clearer management of the cache state. Now, cache are created clean, cache update mark them dirty, writing them on disk mark them clean again.

branchcache: write branchmap in subset inheritance order This way, we can guarantee a valid subset has been written before touching the branchmap of another filter. This is especially useful as we are bout to start deleting outdated branchmap file.

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.

stream-clone-test: simplify case testing obsolescence There is only two important things in this test: - the number of file we send, to show we picked the obsstore. - the resulting state, to show we did alter things in the process. The rest are of the number are very fragile and consume a lot of time for little value when adjusting formats, caches, and protocol.

stream-clone-test: simplify the case testing phases There is only two important things in this test: - the number of file we send, to show we picked the phase roots. - the resulting phases, to show we did not modified them. The rest are of the number are very fragile and consume a lot of time for little value when adjusting formats, caches, and protocol.

stream-clone-test: simplify bookmark clone The important things to test here is the number of file included (to catch that the bookmark file was sent). So we keep that part non glob'ed but glob the rest. The glob'ed numbers are very fragile and consume a lot of time for little value when adjusting formats, caches, and protocol.

stream-clone-test: add a verify call to the "clone while changing" case It seems useful to very that the clone did not result in a corrupted copy.

stream-clone-test: add title to various test cases These case are fine as is, but as we are adding title to all the other as we simplify them, lets add title for all cases.