Prevent auto-fill from creating Org line breaks

* lisp/org.el (org-fill-line-break-nobreak-p): New function.
(org-set-autofill-regexps): Add previous function to
`fill-nobreak-predicate'.

lisp/org.el

@@ -20296,10 +20296,11 @@ the functionality can be provided as a fall-back.")
   (org-set-local 'fill-paragraph-function 'org-fill-paragraph)
   ;; Prevent auto-fill from inserting unwanted new items.
   (if (boundp 'fill-nobreak-predicate)
-      (org-set-local 'fill-nobreak-predicate
-		     (if (memq 'org-fill-item-nobreak-p fill-nobreak-predicate)
-			 fill-nobreak-predicate
-		       (cons 'org-fill-item-nobreak-p fill-nobreak-predicate))))
+      (org-set-local
+       'fill-nobreak-predicate
+       (org-uniquify
+	(append fill-nobreak-predicate
+		'(org-fill-item-nobreak-p org-fill-line-break-nobreak-p)))))
   ;; Adaptive filling: To get full control, first make sure that
   ;; `adaptive-fill-regexp' never matches.  Then install our own matcher.
   (unless (local-variable-p 'adaptive-fill-regexp (current-buffer))
@@ -20319,6 +20320,13 @@ the functionality can be provided as a fall-back.")
   "Non-nil when a line break at point would insert a new item."
   (and (looking-at (org-item-re)) (org-list-in-valid-context-p)))
 
+(defun org-fill-line-break-nobreak-p ()
+  "Non-nil when a line break at point would create an Org line break."
+  (save-excursion
+    (skip-chars-backward "[ \t]")
+    (skip-chars-backward "\\\\")
+    (looking-at "\\\\\\\\\\($\\|[^\\\\]\\)")))
+
 (defun org-fill-paragraph (&optional justify)
   "Re-align a table, pass through to fill-paragraph if no table."
   (let ((table-p (org-at-table-p))