Publish: allow dynamic construction of the publish destination.

* org-publish.el (org-publish-file): Added 'eval'ing the value of the
 :publishing-directory property before using it as destination of the
 publishing project. This allows to construct the publish destination
 directory dynamically at run-time using the return value of a
 function.

TINYCHANGE
---
 lisp/org-publish.el |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/lisp/org-publish.el b/lisp/org-publish.el
index e2213c5..518c1bf 100644
--- a/lisp/org-publish.el
+++ b/lisp/org-publish.el
@@ -684,7 +684,7 @@ See `org-publish-projects'."
 	 (pub-dir
 	  (file-name-as-directory
 	   (file-truename
-	    (or (plist-get project-plist :publishing-directory)
+	    (or (eval (plist-get project-plist :publishing-directory))
 		(error "Project %s does not have :publishing-directory defined"
 		       (car project))))))
 	 tmp-pub-dir)
-- 
1.7.5.4