The rather cryptic:

      "fk_#{Digest::SHA256.hexdigest("#{table}_#{column}_fk").first(10)}"

Was too much for emacs too handle*, since it was coming from the Rails
codebase I took their way of doing the same thing and applied it here.

I think it's easier to read and it also makes emacs render the
migration helpers pretty again.

* not true, emacs can handle anything, leave emacs alone!