Merge branch 'ab/userdiff-tests'

A bit of code clean-up and a lot of test clean-up around userdiff area. * ab/userdiff-tests: blame tests: simplify userdiff driver test blame tests: don't rely on t/t4018/ directory userdiff: remove support for "broken" tests userdiff tests: list builtin drivers via test-tool userdiff tests: explicitly test "default" pattern userdiff: add and use for_each_userdiff_driver() userdiff style: normalize pascal regex declaration userdiff style: declare patterns with consistent style userdiff style: re-order drivers in alphabetical order