branch(.) is not cheap since it builds the revbranchcache:
66 \ branch (2 times) revset.py:465 48 \ wrapper (2 times) localrepo.py:141 48 | revbranchcache (2 times) localrepo.py:959 46 | __init__ branchmap.py:354 16 | read (2 times) vfs.py:78 18 \ branchmap (2 times) localrepo.py:953