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.
http://mercurial.selenic.com/bts/issue619
$ hg init
$ echo a > a
$ hg ci -Ama
adding a
$ echo b > b
$ hg branch b
marked working directory as branch b
(branches are permanent and global, did you want a bookmark?)
$ hg ci -Amb
adding b
$ hg co -C 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
Fast-forward:
$ hg merge b
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg ci -Ammerge
Bogus fast-forward should fail:
$ hg merge b
abort: merging with a working directory ancestor has no effect
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