(do-auto-fill): Look at 2nd line for fill prefix

even when on the first line.  Don't accept non-whitespace prefix
from the first line.

(do-auto-fill): Ignore the result of fill-context-prefix if it is empty.

1 files changed, 9 insertions, 4 deletions

diff --git a/lisp/simple.el b/lisp/simple.el
index 9d34a467d96..fa442280255 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -2331,10 +2331,15 @@ Setting this variable automatically makes it local to the current buffer.")
       ;; Choose a fill-prefix automatically.
       (if (and adaptive-fill-mode
                (or (null fill-prefix) (string= fill-prefix "")))
-          (setq fill-prefix
-                (fill-context-prefix 
-                 (save-excursion (backward-paragraph 1) (point))
-                 (point))))
+          (let ((prefix
+                 (fill-context-prefix
+                  (save-excursion (backward-paragraph 1) (point))
+                  (save-excursion (forward-paragraph 1) (point))
+                  ;; Don't accept a non-whitespace fill prefix
+                  ;; from the first line of a paragraph.
+                  "^[ \t]*$")))
+            (and prefix (not (equal prefix ""))
+                 (setq fill-prefix prefix))))
 
       (while (and (not give-up) (> (current-column) fc))
         ;; Determine where to split the line.