(canonically-space-region): Doc fix.

(fill-context-prefix): If the second line has the first line prefix,
plus whitespace, use the part that the first line shares.
(fill-individual-paragraphs): When prefix changes,
usually get the new prefix from just one line,
with an exception for indented first lines of paragraphs.
Start a new paragraph when a line has extra indentation
after the fill prefix.

1 files changed, 48 insertions, 9 deletions

diff --git a/lisp/textmodes/fill.el b/lisp/textmodes/fill.el
index 5fd50ecc521..4741c0ffdc7 100644
--- a/lisp/textmodes/fill.el
+++ b/lisp/textmodes/fill.el
@@ -136,7 +136,7 @@ number equals or exceeds the local fill-column - right-margin difference."
 (defun canonically-space-region (beg end)
   "Remove extra spaces between words in region.
 Leave one space between words, two at end of sentences or after colons
-(depending on values of `sentence-end-double-space' and `colon-double-space').
+\(depending on values of `sentence-end-double-space' and `colon-double-space').
 Remove indentation from each line."
   (interactive "r")
   (save-excursion
@@ -217,7 +217,14 @@ act as a paragraph-separator."
                                      first-line-prefix)
                        ;; If the second line prefix is whitespace, use it.
                        (string-match "\\`[ \t]+\\'" second-line-prefix))
-                   second-line-prefix))
+                   second-line-prefix
+                 ;; If the second line has the first line prefix,
+                 ;; plus whitespace, use the part that the first line shares.
+                 (if (string-match (concat "\\`"
+                                             (regexp-quote first-line-prefix)
+                                             "[ \t]*\\'")
+                                   second-line-prefix)
+                     first-line-prefix)))
         ;; If we get a fill prefix from a one-line paragraph,
         ;; maybe change it to whitespace,
         ;; and check that it isn't a paragraph starter.
@@ -915,10 +922,19 @@ MAIL-FLAG for a mail message, i. e. don't fill header lines."
 (defun fill-individual-paragraphs (min max &optional justify mailp)
   "Fill paragraphs of uniform indentation within the region.
 This command divides the region into \"paragraphs\", 
-treating every change in indentation level as a paragraph boundary,
+treating every change in indentation level or prefix as a paragraph boundary,
 then fills each paragraph using its indentation level as the fill prefix.
 
-When calling from a program, pass range to fill as first two arguments.
+There is one special case where a change in indentation does not start
+a new paragraph.  This is for text of this form:
+
+   foo>    This line with extra indentation starts
+   foo> a paragraph that continues on more lines.
+
+These lines are filled together.
+
+When calling from a program, pass the range to fill
+as the first two arguments.
 
 Optional third and fourth arguments JUSTIFY and MAIL-FLAG:
 JUSTIFY to justify paragraphs (prefix arg),
@@ -957,10 +973,32 @@ MAIL-FLAG for a mail message, i. e. don't fill header lines."
                    (if (not (and fill-prefix
                                  (looking-at fill-prefix-regexp)))
                        (setq fill-prefix
-                             (or (let ((adaptive-fill-first-line-regexp ""))
-                                   (fill-context-prefix
-                                    (point)
-                                    (save-excursion (forward-line 2) (point))))
+                             ;; Get the prefix from just the first line
+                             ;; ordinarily.
+                             ;; But if using two lines gives us a shorter
+                             ;; result, lacking some whitespace at the end,
+                             ;; use that.
+                             (or (let ((adaptive-fill-first-line-regexp "")
+                                       just-one-line-prefix
+                                       two-lines-prefix)
+                                   (setq just-one-line-prefix
+                                         (fill-context-prefix
+                                          (point)
+                                          (save-excursion (forward-line 1)
+                                                          (point))))
+                                   (setq two-lines-prefix
+                                         (fill-context-prefix
+                                          (point)
+                                          (save-excursion (forward-line 2)
+                                                          (point))))
+                                   (if (and just-one-line-prefix
+                                            two-lines-prefix
+                                            (string-match (concat "\\`"
+                                                                  (regexp-quote two-lines-prefix)
+                                                                  "[ \t]*\\'")
+                                                          just-one-line-prefix))
+                                       two-lines-prefix
+                                     just-one-line-prefix))
                                  (buffer-substring 
                                   (point)
                                   (save-excursion (skip-chars-forward " \t")
@@ -987,7 +1025,8 @@ MAIL-FLAG for a mail message, i. e. don't fill header lines."
                           (and (looking-at fill-prefix-regexp)
                                (save-excursion
                                  (not (progn (forward-char (length fill-prefix))
-                                             (or (looking-at paragraph-separate)
+                                             (or (looking-at "[ \t]")
+                                                 (looking-at paragraph-separate)
                                                  (looking-at paragraph-start))))))))))
           ;; Fill this paragraph, but don't add a newline at the end.
           (let ((had-newline (bolp)))