Also look in Homebrew/homebrew-core for uncommitted files (in some ways
we care about uncommitted stuff there more than Homebrew/brew). Also,
list all the modified files even when on non-CI to make it easier for
users to figure out their own issues and check the contents of the
whole repos rather than just a subdirectory.

In general this is a cleanup that should have been done long ago (when
we split Homebrew/brew and Homebrew/homebrew-core).