Don't create UID for the entire file when write an agenda to .ics

* org-agenda.el (org-agenda-collect-markers)
(org-create-marker-find-array): Move to ox-icalendar.el.
(org-agenda-marker-table, org-check-agenda-marker-table):
Delete.

* ox-icalendar.el (org-icalendar-create-uid): New parameter
H-MARKERS to only update some headlines, not the whole file.
(org-icalendar--combine-files): When exporting to an .ics file
only add UID to the headlines shown in the agenda buffer.
(org-agenda-collect-markers, org-create-marker-find-array):
Move here.

lisp/org-agenda.el

@@ -3432,43 +3432,6 @@ removed from the entry content.  Currently only `planning' is allowed here."
 		(setq txt (buffer-substring (point-min) (point)))))))))
     txt))
 
-(defun org-agenda-collect-markers ()
-  "Collect the markers pointing to entries in the agenda buffer."
-  (let (m markers)
-    (save-excursion
-      (goto-char (point-min))
-      (while (not (eobp))
-	(when (setq m (or (org-get-at-bol 'org-hd-marker)
-			  (org-get-at-bol 'org-marker)))
-	  (push m markers))
-	(beginning-of-line 2)))
-    (nreverse markers)))
-
-(defun org-create-marker-find-array (marker-list)
-  "Create a alist of files names with all marker positions in that file."
-  (let (f tbl m a p)
-    (while (setq m (pop marker-list))
-      (setq p (marker-position m)
-	    f (buffer-file-name (or (buffer-base-buffer
-				     (marker-buffer m))
-				    (marker-buffer m))))
-      (if (setq a (assoc f tbl))
-	  (push (marker-position m) (cdr a))
-	(push (list f p) tbl)))
-    (mapcar (lambda (x) (setcdr x (sort (copy-sequence (cdr x)) '<)) x)
-	    tbl)))
-
-(defvar org-agenda-marker-table nil) ; dynamically scoped parameter
-(defun org-check-agenda-marker-table ()
-  "Check of the current entry is on the marker list."
-  (let ((file (buffer-file-name (or (buffer-base-buffer) (current-buffer))))
-	a)
-    (and (setq a (assoc file org-agenda-marker-table))
-	 (save-match-data
-	   (save-excursion
-	     (org-back-to-heading t)
-	     (member (point) (cdr a)))))))
-
 (defun org-check-for-org-mode ()
   "Make sure current buffer is in org-mode.  Error if not."
   (or (derived-mode-p 'org-mode)

lisp/ox-icalendar.el

@@ -285,20 +285,23 @@ re-read the iCalendar file.")
 
 ;;; Internal Functions
 
-(defun org-icalendar-create-uid (file &optional bell)
+(defun org-icalendar-create-uid (file &optional bell h-markers)
   "Set ID property on headlines missing it in FILE.
 When optional argument BELL is non-nil, inform the user with
-a message if the file was modified."
-  (let (modified-flag)
+a message if the file was modified.  With optional argument
+H-MARKERS non-nil, it is a list of markers for the headlines
+which will be updated."
+  (let (modified-flag pt)
+    (when h-markers (setq pt (goto-char (car h-markers))))
     (org-map-entries
      (lambda ()
        (let ((entry (org-element-at-point)))
-	 (unless (org-element-property :ID entry)
+	 (unless (or (< (point) pt) (org-element-property :ID entry))
 	   (org-id-get-create)
 	   (setq modified-flag t)
 	   (forward-line))
-	 (when (eq (org-element-type entry) 'inlinetask)
-	   (setq org-map-continue-from (org-element-property :end entry)))))
+	 (setq org-map-continue-from
+	       (if h-markers (pop h-markers) (point-max)))))
      nil nil 'comment)
     (when (and bell modified-flag)
       (message "ID properties created in file \"%s\"" file)
@@ -888,8 +891,32 @@ The file is stored under the name chosen in
 	  `(apply 'org-icalendar--combine-files nil ',files)))
     (apply 'org-icalendar--combine-files nil (org-agenda-files t))))
 
-(declare-function org-agenda-collect-markers "org-agenda" ())
-(declare-function org-create-marker-find-array "org-agenda" (marker-list))
+(defun org-agenda-collect-markers ()
+  "Collect the markers pointing to entries in the agenda buffer."
+  (let (m markers)
+    (save-excursion
+      (goto-char (point-min))
+      (while (not (eobp))
+	(when (setq m (or (org-get-at-bol 'org-hd-marker)
+			  (org-get-at-bol 'org-marker)))
+	  (push m markers))
+	(beginning-of-line 2)))
+    (nreverse markers)))
+
+(defun org-create-marker-find-array (marker-list)
+  "Create an alist of files names with all marker positions in that file."
+  (let (f tbl m a p)
+    (while (setq m (pop marker-list))
+      (setq p (marker-position m)
+	    f (buffer-file-name
+	       (or (buffer-base-buffer (marker-buffer m))
+		   (marker-buffer m))))
+      (if (setq a (assoc f tbl))
+	  (push (marker-position m) (cdr a))
+	(push (list f p) tbl)))
+    (mapcar (lambda (x) (setcdr x (sort (copy-sequence (cdr x)) '<)) x)
+	    tbl)))
+
 (defun org-icalendar-export-current-agenda (file)
   "Export current agenda view to an iCalendar FILE.
 This function assumes major mode for current buffer is
@@ -930,11 +957,10 @@ files to build the calendar from."
 		(catch 'nextfile
 		  (org-check-agenda-file file)
 		  (with-current-buffer (org-get-agenda-file-buffer file)
-		    ;; Create ID if necessary.
-		    (when org-icalendar-store-UID
-		      (org-icalendar-create-uid file))
-		    (let ((marks (cdr (assoc (expand-file-name file)
-					     restriction))))
+		    (let ((marks (cdr (assoc (expand-file-name file) restriction))))
+		      ;; Create ID if necessary.
+		      (when org-icalendar-store-UID
+			(org-icalendar-create-uid file t marks))
 		      (unless (and restriction (not marks))
 			;; Add a hook adding :ICALENDAR_MARK: property
 			;; to each entry appearing in agenda view.