bug#3863: 23.1.50; possible save-match-data in copyright.el

[Kevin Ryde]

In recent copyright.el I noticed copyright-update using the match data
after a y-or-n-p query.  Is that a good idea?

When running it in emacs 22 I seemed to sometimes get the match data
clobbered by y-or-n-p.  I never tracked down the circumstances, but
wondered if copyright.el shouldn't rely on what an input func like
y-or-n-p could do, per diff below.


In GNU Emacs 23.1.50.1 (i586-pc-linux-gnu, GTK+ Version 2.16.4)
 of 2009-07-12 on blah.blah
configured using `configure  'CFLAGS=-O -g' '--prefix=/down/emacs/b/inst' 
'--with-x-toolkit=gtk''

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


2009-07-16  Kevin Ryde  <user42@zip.com.au>

        * emacs-lisp/copyright.el (copyright-update): save-match-data across
        y-or-n-p, for safety.

*** copyright.el        16 Jul 2009 09:44:20 +1000      1.81
--- copyright.el        16 Jul 2009 09:55:57 +1000      
***************
*** 223,230 ****
                 (< (string-to-number (match-string 3))
                    (string-to-number copyright-current-gpl-version))
               (or noquery
!                  (y-or-n-p (format "Replace GPL version by %s? "
!                                    copyright-current-gpl-version)))
               (progn
                 (if (match-end 2)
                     ;; Esperanto bilingual comment in two-column.el
--- 223,231 ----
                 (< (string-to-number (match-string 3))
                    (string-to-number copyright-current-gpl-version))
               (or noquery
!                    (save-match-data
!                      (y-or-n-p (format "Replace GPL version by %s? "
!                                        copyright-current-gpl-version))))
               (progn
                 (if (match-end 2)
                     ;; Esperanto bilingual comment in two-column.el