org-babel: improve prompt when choosing file to tangle

contrib/babel/lisp/org-babel-tangle.el

@@ -62,7 +62,7 @@ file using `load-file'."
 specify a default export file for all source blocks.  Optional
 argument LANG can be used to limit the exported source code
 blocks by language."
-  (interactive "f")
+  (interactive "fFile to tangle: \nP")
   (save-window-excursion (find-file file) (org-babel-tangle target-file lang)))
 
 (defun org-babel-tangle (&optional target-file lang)