ffap-file-exists-string
ffap-file-exists-string is a compiled Lisp function in `ffap.el
'.
(ffap-file-exists-string FILE &optional NOMODIFY)
Return FILE (maybe modified) if the file exists, else nil.
When using jka-compr (a.k.a. `auto-compression-mode'), the returned
name may have a suffix added from `ffap-compression-suffixes'.
The optional NOMODIFY argument suppresses the extra search.