pathname-as-dir - return a `pathname` directory

pathname-as-dir.lisp

;; `(pathname "/foo/bar")` uses the trailing directory separator to decide if a
;; path refers to a file or directory

;; (pathname "/home/foo.bar" ) => #P"/home/foo.bar"

;; (pathname "/home/foo.bar/") => #P"/home/foo.bar/"

;; Instead, this function definition `pathname-as-dir` results in a pathname
;; which is a always a directory irrespective of the trailing slash contained in
;; the string argument.

;; (pathname-as-dir "/foo/foo.bar")  => #P"/foo/foo.bar/"
;; (pathname-as-dir "/foo/foo.bar/") => #P"/foo/foo.bar/" 

;; Instead of using this snippet, you should use `cl-fad:pathname-as-directory`
;; which is part of the robust `cl-fad` library.

;; This below snippet was useful where `cl-fad` could not be loaded in an early
;; setup stage (although there might be a way to do it)

(defun pathname-as-dir (path)
  (let* ((p (pathname path))
         (dir (or (pathname-directory p) (list :relative)))
         (type (pathname-type p))
         (suffix (when type (concatenate 'string "." type)))
         (name (concatenate 'string (pathname-name p) suffix)))
    (make-pathname :directory
                   (if name (append dir (list name)) dir)
                   :name nil
                   :type nil
                   :defaults p)))