Make icalendar-import-buffer not show diary file buffer

* lisp/calendar/diary-lib.el (diary-make-entry): Add
omit-trailing-space parameter.  Add do-not-show parameter to
allow not showing diary file buffer.
* lisp/calendar/icalendar.el (icalendar--add-diary-entry): Remove
workaround to omit trailing space in diary entry.  Have
diary-make-entry not display the diary file buffer.  (Bug#35645)

lisp/calendar/diary-lib.el

@@ -2062,27 +2062,34 @@ calendar."
 ;;; Diary insertion functions.
 
 ;;;###cal-autoload
-(defun diary-make-entry (string &optional nonmarking file)
+(defun diary-make-entry (string &optional nonmarking file omit-trailing-space
+                                do-not-show)
   "Insert a diary entry STRING which may be NONMARKING in FILE.
 If omitted, NONMARKING defaults to nil and FILE defaults to
-`diary-file'."
-  (let ((pop-up-frames (or pop-up-frames (window-dedicated-p))))
-    (find-file-other-window (or file diary-file)))
-  (when (eq major-mode (default-value 'major-mode)) (diary-mode))
-  (widen)
-  (diary-unhide-everything)
-  (goto-char (point-max))
-  (when (let ((case-fold-search t))
-          (search-backward "Local Variables:"
-                           (max (- (point-max) 3000) (point-min))
-                           t))
-    (beginning-of-line)
-    (insert "\n")
-    (forward-line -1))
-  (insert
-   (if (bolp) "" "\n")
-   (if nonmarking diary-nonmarking-symbol "")
-   string " "))
+`diary-file'.  If OMIT-TRAILING-SPACE is non-nil, then do not add
+a trailing space to the entry.  If DO-NOT-SHOW is non-nil, do not
+show the diary buffer."
+  (with-current-buffer
+      (let ((diary-file-name (or file diary-file)))
+        (if do-not-show
+            (find-file-noselect diary-file-name)
+          (let ((pop-up-frames (or pop-up-frames (window-dedicated-p))))
+            (find-file-other-window diary-file-name))))
+    (when (eq major-mode (default-value 'major-mode)) (diary-mode))
+    (widen)
+    (diary-unhide-everything)
+    (goto-char (point-max))
+    (when (let ((case-fold-search t))
+            (search-backward "Local Variables:"
+                             (max (- (point-max) 3000) (point-min))
+                             t))
+      (beginning-of-line)
+      (insert "\n")
+      (forward-line -1))
+    (insert
+     (if (bolp) "" "\n")
+     (if nonmarking diary-nonmarking-symbol "")
+     string (if omit-trailing-space "" " "))))
 
 ;;;###cal-autoload
 (defun diary-insert-entry (arg &optional event)

lisp/calendar/icalendar.el

@@ -2502,20 +2502,10 @@ the entry."
     (when summary
       (setq non-marking
             (y-or-n-p (format "Make appointment non-marking? "))))
-    (save-window-excursion
-      (unless diary-filename
-        (setq diary-filename
-              (read-file-name "Add appointment to this diary file: ")))
-      ;; Note: diary-make-entry will add a trailing blank char.... :(
-      (funcall (if (fboundp 'diary-make-entry)
-                   'diary-make-entry
-                 'make-diary-entry)
-               string non-marking diary-filename)))
-  ;; Würgaround to remove the trailing blank char
-  (with-current-buffer (find-file diary-filename)
-    (goto-char (point-max))
-    (if (= (char-before) ? )
-        (delete-char -1)))
+    (unless diary-filename
+      (setq diary-filename
+            (read-file-name "Add appointment to this diary file: ")))
+    (diary-make-entry string non-marking diary-filename t t))
   ;; return diary-filename in case it has been changed interactively
   diary-filename)