bug#6206: 23.1; docstring info node links with newlines

[Kevin Ryde]

In a docstring has an info link with a newline in it like

(defun foo ()
  "Foo.
Info node `(emacs)File
Variables'."
  nil)

The link is buttonized by M-x describe-function, but pressing Ret on the
button gets an error

    No such node or anchor: File

The end of `gnus-level-unsubscribed' is an example of this -- though it
has a separate problem of needing the manual name `(gnus)Group Levels'.


2010-05-18  Kevin Ryde  <user42@zip.com.au>

        * help-mode.el (help-make-xrefs): For info node links turn
        newlines into spaces.  Link node names with newlines are matched
        by help-xref-info-regexp and buttonized, this change ensures they
        can be followed successfully with Ret.

--- help-mode.el.~1.71.~        2009-11-17 10:41:35.000000000 +1100
+++ help-mode.el        2010-05-18 10:39:27.000000000 +1000
@@ -433,7 +433,9 @@
                     (let ((data (match-string 2)))
                       (save-match-data
                         (unless (string-match "^([^)]+)" data)
-                          (setq data (concat "(emacs)" data))))
+                          (setq data (concat "(emacs)" data)))
+                       (setq data ;; possible newlines if para filled
+                             (replace-regexp-in-string "\n" " " data t t)))
                       (help-xref-button 2 'help-info data))))
                 ;; URLs
                 (save-excursion


In GNU Emacs 23.1.1 (i486-pc-linux-gnu, GTK+ Version 2.16.5)
 of 2009-09-14 on raven, modified by Debian
configured using `configure  '--build=i486-linux-gnu' '--host=i486-linux-gnu' 
'--prefix=/usr' '--sharedstatedir=/var/lib' '--libexecdir=/usr/lib' 
'--localstatedir=/var/lib' '--infodir=/usr/share/info' 
'--mandir=/usr/share/man' '--with-pop=yes' 
'--enable-locallisppath=/etc/emacs23:/etc/emacs:/usr/local/share/emacs/23.1/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/23.1/site-lisp:/usr/share/emacs/site-lisp:/usr/share/emacs/23.1/leim'
 '--with-x=yes' '--with-x-toolkit=gtk' '--with-toolkit-scroll-bars' 
'build_alias=i486-linux-gnu' 'host_alias=i486-linux-gnu' 'CFLAGS=-DDEBIAN -g 
-O2' 'LDFLAGS=-g' 'CPPFLAGS=''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_AU
  value of $XMODIFIERS: nil
  locale-coding-system: iso-latin-1-unix
  default-enable-multibyte-characters: t