branchmap: `stream_in` write remote branchcache to local one The previous code was writing it to a non existent `branchcache` attribute. We now write is to the proper `_branchcache` attribute and initialize the `_branchcachetip` at the same time. We keep writing it to disk, the previous code had this part right.

bookmarks: fix head selection for merge with two bookmarked heads A type mismatch caused the search for the other head to fail. The code is fragile, and instead it ended up using the 'first' bookmark head, but the ordering is undefined and it could thus randomly use the wrong bookmarkhead and fail with: $ hg up -q -C e@diverged $ hg merge abort: merging with a working directory ancestor has no effect

branchmap: extract updatebranchcache from repo

branchmap: extract _updatebranchcache from repo

branchmap: _updatebranchmap does not need to be filtered The `_updatebranchmap` method on repo does not need to be filtered as all callers are already handling filtering themself. The fact it is filtered may had even lead to buggy behaviors, but by chances the method make very sparse use of the repo object.

branchmap: extract read logic from repo