Currently, the `.arcunit` files use this rule:
"include": "(\\.php$)"
However, this means that the tests don't run if you only touch unit test data files which don't end in `.php`. For example, in D13992 I touched two test cases that are in `.lint-test` files, but that touch didn't trigger the tests to run on `arc unit`. It seems like it should, since I directly changed the tests and the standard rules can discover the correct tests to run on this data.
We could use the rule `(^src/)` instead, or possibly just `(.*)` (or maybe we can omit it entirely, I don't recall the behavior of no rule).
See some prior discussion in D13853. Maybe `(.*)` is best?