tests: add a metaclass for testing obsolete mode We use a metaclass to both make the test code more concise, and more likely to cover all cases. Typically, someone adding a new fixes will also add a test, and put it in a class containing similar tests. Going forward, having that entire class automatically then duplicate its methods for relevant modes is a plus; a similar approach for stupid mode already found a few omissions.

include Makefile hgsubversion/help/*.rst tests/fixtures/invalid_utf8.tar.gz
recursive-include tests *.py *.sh *.svndump *.txt