[Orgmode] Hide tasks from the agenda until they are due

[PT]

In a previous thread
(http://thread.gmane.org/gmane.emacs.orgmode/17818) there was a
discussion about using the agenda to schedule trivial time-specific
tasks during the day which can be done at or after a certain
time. These tasks should be hidden from the agenda until their time is
due, because you cannot work on them before then, so they are just
polluting the agenda view.

Matt Lundin kindly provided a quick untested solution in that thread
which was almost complete, it needed only a bit of tweaking. Here is 
the working solution (not yes extensively tested) for those interested:


    (defun my-org-agenda-skip-if-later ()
      "Skip entries that are later than the current time."
      (let ((time (and (org-entry-get nil "TIME-TODO")
                       (or (org-entry-get nil "TIMESTAMP")
                           (org-entry-get nil "SCHEDULED")))))
        (when time
          (unless (time-less-p (org-time-string-to-time time) (current-time))
            (or (outline-next-heading)
                (point-max))))))

    (setq org-agenda-skip-function 'my-org-agenda-skip-if-later)


The tasks to be hidden need to have a special property set (TIME-TODO)
in order to distinguish them from regular timestamps which are not hidden. 
I added this property to my remember template, so it's automatically 
set when I create such a task.

I set the skip function globally, because I use a single agenda view. You
may want to set it only for certain agenda views.