While addressing ASDF [issue #140](https://gitlab.common-lisp.net/asdf/asdf/-/issues/140) I stumbled on what seems to me to be an error. That is that (ensure-directory-pathname "") at least on SBCL, returns a `pathname` that has `NIL` in all its slots except `HOST`. To me, this seemed wrong, and looking further, I found that `directory-pathname-p` returns `T` when given this pathname, because `directory-pathname-p` is defined (in its docstring) as:
A directory-pathname is a pathname _without_ a filename.
I would have assumed that a directory pathname was *also* a pathname with a non-`NIL` `directory` component. I am considering making this (incompatible) change, but am interested in any feedback about whether this is the correct thing to do.