Backport commit 74b8615fc from Emacs

* lisp/ob-tangle.el (org-babel-tangle-publish): Port to new copy-file
behavior.

Adjust ob-tangle to new copy-file behavior
74b8615fcceba7b92c4938e1bcc92015f10ae899
Paul Eggert
Sun Sep 10 22:31:23 2017 -0700

lisp/ob-tangle.el

@@ -196,6 +196,7 @@ Return a list whose CAR is the tangled file name."
   "Tangle FILENAME and place the results in PUB-DIR."
   (unless (file-exists-p pub-dir)
     (make-directory pub-dir t))
+  (setq pub-dir (file-name-as-directory pub-dir))
   (mapc (lambda (el) (copy-file el pub-dir t)) (org-babel-tangle-file filename)))
 
 ;;;###autoload