url-expand-file-name

url-expand-file-name is an autoloaded compiled Lisp function in `url-expand.el'.

(url-expand-file-name URL &optional DEFAULT)

Convert URL to a fully specified URL, and canonicalize it.
Second arg DEFAULT is a URL to start with if URL is relative.
If DEFAULT is nil or missing, the current buffer's URL is used.
Path components that are `.' are removed, and
path components followed by `..' are removed, along with the `..' itself.