Auto-fill shouldn't insert new items

* lisp/org-list.el (org-list-in-valid-context-p): renamed from
  org-list-in-valid-block-p.
  (org-at-item-p,org-list-search-generic): use renamed function.

* lisp/org.el (org-fill-item-nobreak-p): new function.
  (org-set-autofill-regexps): modify `fill-nobreak-predicate' to
  prevent auto-fill from breaking line just before an item regexp.

lisp/org-list.el

@@ -401,7 +401,7 @@ group 4: description tag")
            (goto-char (match-end 0)))
 	 (looking-at regexp))))
 
-(defun org-list-in-valid-block-p ()
+(defun org-list-in-valid-context-p ()
   "Non-nil if point is in a valid block.
 Invalid blocks are referring to `org-list-forbidden-blocks'."
   (save-match-data
@@ -491,7 +491,7 @@ This checks `org-list-ending-method'."
   "Is point in a line starting a hand-formatted item?"
   (save-excursion
     (beginning-of-line)
-    (and (looking-at (org-item-re)) (org-list-in-valid-block-p))))
+    (and (looking-at (org-item-re)) (org-list-in-valid-context-p))))
 
 (defun org-at-item-bullet-p ()
   "Is point at the bullet of a plain list item?"
@@ -1053,7 +1053,7 @@ in `re-search-forward'."
 			    nil)))
 	;; 2. Match in valid context: return point. Else, continue
 	;;    searching.
-	(when (org-list-in-valid-block-p) (throw 'exit (point)))))))
+	(when (org-list-in-valid-context-p) (throw 'exit (point)))))))
 
 (defun org-list-search-backward (regexp &optional bound noerror)
   "Like `re-search-backward' but stop only where lists are recognized.

lisp/org.el

@@ -19180,6 +19180,11 @@ the functionality can be provided as a fall-back.")
   ;; and fixed-width regions are not wrapped.  That function will pass
   ;; through to `fill-paragraph' when appropriate.
   (org-set-local 'fill-paragraph-function 'org-fill-paragraph)
+  ;; Prevent auto-fill from inserting unwanted new items.
+  (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)))
   ;; 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))
@@ -19195,6 +19200,10 @@ the functionality can be provided as a fall-back.")
       (regexp . "^#\\+[A-Z_]+:\\(\\s-*\\)\\S-+")
       (modes . '(org-mode))))))
 
+(defun org-fill-item-nobreak-p ()
+  "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-paragraph (&optional justify)
   "Re-align a table, pass through to fill-paragraph if no table."
   (let ((table-p (org-at-table-p))