bug#74627: .dir-locals.el warning messages are confusing

[Stefan Monnier]

>> Regardless of whether my guess is correct, the text should
>> not refer to the local variables in "/home/bjourne/p/emacs/" because
>> there can be no unsafe variables in directories (only files).
> Well, we consider variables in .dir-locals.el as belonging to the
> directory in which it lives.

I think it would be easier to understand for the reader if we can point
more precisely to the source (especially since now it can also come
from `.editorconfig`).


        Stefan