* isearch.el (isearch-allow-prefix): New user option.

        (isearch-other-meta-char): don't exit isearch when a prefix
        argument is typed whilst `isearch-allow-prefix' is non-nil.

        * search.texi (Isearch Scroll): Rename to "Not Exiting Isearch".
        (Net Exiting Isearch): Document new user option
        `isearch-allow-prefix'.

	* etc/NEWS.  Entry for this change.

2 files changed, 27 insertions, 6 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 7de7b079570..f40a23a5035 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,9 @@
+2013-06-05  Alan Mackenzie  <acm@muc.de>
+
+        * isearch.el (isearch-allow-prefix): New user option.
+        (isearch-other-meta-char): don't exit isearch when a prefix
+        argument is typed whilst `isearch-allow-prefix' is non-nil.
+
 2013-06-05  Stefan Monnier  <monnier@iro.umontreal.ca>
 
         * autorevert.el (auto-revert-notify-handler): Use memq.
diff --git a/lisp/isearch.el b/lisp/isearch.el
index c49b0d7fc59..e6678d33ea4 100644
--- a/lisp/isearch.el
+++ b/lisp/isearch.el
@@ -2152,6 +2152,14 @@ If nil, scrolling commands will first cancel Isearch mode."
   :type 'boolean
   :group 'isearch)
 
+(defcustom isearch-allow-prefix t
+  "Whether prefix arguments are allowed during incremental search.
+If non-nil, entering a prefix argument will not terminate the
+search.  This option is ignored \(presumed t) when
+`isearch-allow-scroll' is set."
+  :type 'boolean
+  :group 'isearch)
+
 (defun isearch-string-out-of-window (isearch-point)
   "Test whether the search string is currently outside of the window.
 Return nil if it's completely visible, or if point is visible,
@@ -2304,12 +2312,19 @@ Isearch mode."
            (setq prefix-arg arg)
            (apply 'isearch-unread keylist)
            (isearch-edit-string))
-          ;; Handle a scrolling function.
-          ((and isearch-allow-scroll
-                (progn (setq key (isearch-reread-key-sequence-naturally keylist))
-                       (setq keylist (listify-key-sequence key))
-                       (setq main-event (aref key 0))
-                       (setq scroll-command (isearch-lookup-scroll-key key))))
+          ;; Handle a scrolling function or prefix argument.
+          ((progn
+             (setq key (isearch-reread-key-sequence-naturally keylist)
+                   keylist (listify-key-sequence key)
+                   main-event (aref key 0))
+             (or (and isearch-allow-scroll
+                      (setq scroll-command (isearch-lookup-scroll-key key)))
+                 (and isearch-allow-prefix
+                      (let (overriding-terminal-local-map)
+                        (setq scroll-command (key-binding key))
+                        (memq scroll-command
+                              '(universal-argument
+                                negative-argument digit-argument))))))
            ;; From this point onwards, KEY, KEYLIST and MAIN-EVENT hold a
            ;; complete key sequence, possibly as modified by function-key-map,
            ;; not merely the one or two event fragment which invoked