tests/test-simplemerge.py.out

branchmap: move branch cache code out of streamclone.py

This is low-level branch map and cache manipulation code. It deserves to
live next to similar code in branchmap.py. Moving it also paves the road
for multiple consumers, such as a bundle2 part handler that receives
branch mappings from a remote.

This is largely a mechanical move, with only variable names and
indentation being changed.

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Ran 16 tests in 0.000s

OK