+(defun elpher-collapse-dot-sequences (filename)
+ "Collapse dot sequences in FILENAME.
+For instance, the filename /a/b/../c/./d will reduce to /a/c/d"
+ (let* ((path (split-string filename "/"))
+ (path-reversed-normalized
+ (seq-reduce (lambda (a b)
+ (cond ((and a (equal b "..") (cdr a)))
+ ((and (not a) (equal b "..")) a) ;leading .. are dropped
+ ((equal b ".") a)
+ (t (cons b a))))
+ path nil)))
+ (string-join (reverse path-reversed-normalized) "/")))
+