tests/test-simplemerge.py.out

manifest: make manifest.intersectfiles() internal

manifest.intersectfiles() is just a utility used by manifest.matches(), and
a future commit removes intersectfiles for treemanifest for optimization
purposes.

This commit makes the intersectfiles methods on manifestdict and treemanifest
internal, and converts its test to a more generic testMatches(), which has the
exact same coverage.

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Ran 16 tests in 0.000s

OK