Add help-echo to habit graph

Patch by Michael Fornius.

lisp/ChangeLog

@@ -1,3 +1,8 @@
+2010-05-13  Mikael Fornius  <mfo@abc.se>
+
+	* org-habit.el (org-habit-build-graph): Help-echo date when
+	mouse is over stars.
+
 2010-05-13  Jan Böker  <jan.boecker@jboecker.de>
 
 	* org.el (org-file-apps): Improve docstring to reflect

lisp/org-habit.el

@@ -280,9 +280,16 @@ current time."
 		       donep)))
 	     markedp face)
 	(if donep
-	    (progn
+	    (let ((done-time (time-add
+			      starting
+			      (days-to-time
+			       (- start (time-to-days starting))))))
+
 	      (aset graph index ?*)
 	      (setq markedp t)
+	      (put-text-property
+	       index (1+ index) 'help-echo
+	       (format-time-string (org-time-stamp-format) done-time) graph)
 	      (while (and done-dates
 			  (= start (car done-dates)))
 		(setq last-done-date (car done-dates)