org-agenda.el: Fix bug when using `org-agenda-do-date-later' in filtered agendas

* org-agenda.el (org-agenda-filter-hide-line): Hide from the
beginning of the line to the beginning of the next line.
(org-agenda-show-new-time): Use `move-beginning-of-line' and
`move-end-of-line'.
(org-agenda-drag-line-forward): Adapt to the new definition of
hidden filtered lines.

Thanks to Igor Sosa Mayor for reporting this bug and to Nick Dokos
and Matt Lundin for providing further information.

lisp/org-agenda.el

@@ -7658,8 +7658,8 @@ When NO-OPERATOR is non-nil, do not add the + operator to returned tags."
 (defun org-agenda-filter-hide-line (type)
   "Hide lines with TYPE in the agenda buffer."
   (let (ov)
-    (setq ov (make-overlay (max (point-min) (1- (point-at-bol)))
-			   (point-at-eol)))
+    (setq ov (make-overlay (max (point-min) (point-at-bol))
+			   (1+ (point-at-eol))))
     (overlay-put ov 'invisible t)
     (overlay-put ov 'type type)
     (cond ((eq type 'tag) (push ov org-agenda-tag-filter-overlays))
@@ -9177,8 +9177,8 @@ Called with a universal prefix arg, show the priority instead of setting it."
              (1- (point)) (point-at-eol)
 	     (list 'display (org-add-props stamp nil
 			      'face 'secondary-selection))))
-	  (beginning-of-line 1))
-	(beginning-of-line 0)))))
+	  (move-beginning-of-line 1))
+	(move-beginning-of-line 0)))))
 
 (defun org-agenda-date-prompt (arg)
   "Change the date of this item.  Date is prompted for, with default today.
@@ -9940,23 +9940,25 @@ current HH:MM time."
   "Drag an agenda line forward by ARG lines.
 When the optional argument `backward' is non-nil, move backward."
   (interactive "p")
-  (let ((inhibit-read-only t) lst line)
+  (let ((inhibit-read-only t) lst)
     (if (or (not (get-text-property (point) 'txt))
 	    (save-excursion
 	      (dotimes (n arg)
 		(move-beginning-of-line (if backward 0 2))
+		(forward-char 1)
 		(push (not (get-text-property (point) 'txt)) lst))
 	      (delq nil lst)))
-	(message "Cannot move line forward")
-      (let ((end (save-excursion (move-beginning-of-line 2) (point))))
+	(message "Cannot move line %s" (if backward "backward" "forward"))
+      (let ((end (save-excursion (move-end-of-line 1) (point)))
+	    (col (current-column)) line)
 	(move-beginning-of-line 1)
 	(setq line (buffer-substring (point) end))
-	(delete-region (point) end)
-	(move-beginning-of-line (funcall (if backward '1- '1+) arg))
-	(insert line)
+	(delete-region (point) (1+ end))
+	(move-end-of-line (funcall (if backward '1- '1+) (1- arg)))
+	(insert "\n" line)
+	(org-move-to-column col)
 	(org-agenda-reapply-filters)
-	(org-agenda-mark-clocking-task)
-	(move-beginning-of-line 0)))))
+	(org-agenda-mark-clocking-task)))))
 
 (defun org-agenda-drag-line-backward (arg)
   "Drag an agenda line backward by ARG lines."