branchcache: pass the target repository when copying...
branchcache: pass the target repository when copying
Branchmap are usually copied to be used on a different repoview using a
different filter level. Passing the repository around means the repository in
`branchcache._repo` will drift from the actual branchmap filter.
This is currently "fine" because the repo is only used to retrieve the `nullid`
value. However, this is a fairly big trap for any extension or future code using
the `_repo` attribute.
The replace logic is now using a copy to ensure the right repository view is
used to initialized the cached value.
We add a couple of assert for make sure this inconsistency does not sneak back.
