* lisp/isearch.el (search-exit-option): Add options ‘shift-move’ and ‘move’.

Change type from ‘boolean’ to ‘choice’.  Extend docstring.
(isearch-pre-move-point): New variable.
(isearch-pre-command-hook, isearch-post-command-hook):
Handle search-exit-option for values ‘move’ and ‘shift-move’.

* doc/emacs/search.texi (Not Exiting Isearch): Document new
values ‘shift-move’ and ‘move’ of search-exit-option.

https://lists.gnu.org/archive/html/emacs-devel/2018-03/msg00013.html

doc/emacs/search.texi

@@ -437,7 +437,7 @@ of the keymap @code{isearch-mode-map} (@pxref{Keymaps}).
 
 This subsection describes how to control whether typing a command not
 specifically meaningful in searches exits the search before executing
-the command.  It also describes two categories of commands which you
+the command.  It also describes three categories of commands which you
 can type without exiting the current incremental search, even though
 they are not themselves part of incremental search.
 
@@ -507,6 +507,18 @@ change point, the buffer contents, the match data, the current buffer,
 or the selected window and frame.  The command must not itself attempt
 an incremental search.  This feature is disabled if
 @code{isearch-allow-scroll} is @code{nil} (which it is by default).
+
+@item Motion Commands
+@cindex motion commands, during incremental search
+When @code{search-exit-option} is customized to @code{shift-move},
+you can extend the search string by holding down the shift key while
+typing cursor motion commands.  It will yank text that ends at the new
+position after moving point in the current buffer.
+
+When @code{search-exit-option} is @code{move}, you can extend the
+search string without using the shift key for cursor motion commands,
+but it applies only for certain motion command that have the
+@code{isearch-move} property on their symbols.
 @end table
 
 @node Isearch Minibuffer

etc/NEWS

@@ -180,6 +180,14 @@ created by 'edit-last-kbd-macro', and to save the macro by 'C-c C-c'.
 ---
 *** New filter ibuffer-filter-by-process; bound to '/E'.
 
+** Search and Replace
+
+*** 'search-exit-option' provides new options 'move' and 'shift-move'
+to extend the search string by yanking text that ends at the new
+position after moving point in the current buffer.  'shift-move'
+extends the search string by motion commands while holding down
+the shift key.
+
 ** Edebug
 
 +++

lisp/isearch.el

@@ -67,8 +67,23 @@
 
 
 (defcustom search-exit-option t
-  "Non-nil means random control characters terminate incremental search."
-  :type 'boolean)
+  "Defines what control characters do in incremental search.
+If t, random control and meta characters terminate the search
+and are then executed normally.
+If `edit', edit the search string instead of exiting.
+If `move', extend the search string by motion commands
+that have the `isearch-move' property on their symbols.
+If `shift-move', extend the search string by motion commands
+while holding down the shift key.
+Both `move' and `shift-move' extend the search string by yanking text
+that ends at the new position after moving point in the current buffer.
+If nil, run the command without exiting Isearch."
+  :type '(choice (const :tag "Terminate incremental search" t)
+                 (const :tag "Edit the search string" edit)
+                 (const :tag "Extend the search string by motion commands" move)
+                 (const :tag "Extend the search string by shifted motion keys" shift-move)
+                 (const :tag "Don't terminate incremental search" nil))
+  :version "27.1")
 
 (defcustom search-slow-window-lines 1
   "Number of lines in slow search display windows.
@@ -2391,6 +2406,7 @@ the bottom."
   (goto-char isearch-point))
 
 (defvar isearch-pre-scroll-point nil)
+(defvar isearch-pre-move-point nil)
 
 (defun isearch-pre-command-hook ()
   "Decide whether to exit Isearch mode before executing the command.
@@ -2398,8 +2414,9 @@ Don't exit Isearch if the key sequence that invoked this command
 is bound in `isearch-mode-map', or if the invoked command is
 a prefix argument command (when `isearch-allow-prefix' is non-nil),
 or it is a scrolling command (when `isearch-allow-scroll' is non-nil).
-Otherwise, exit Isearch (when `search-exit-option' is non-nil)
-before the command is executed globally with terminated Isearch."
+Otherwise, exit Isearch (when `search-exit-option' is t)
+before the command is executed globally with terminated Isearch.
+See more for options in `search-exit-option'."
   (let* ((key (this-single-command-keys))
 	 (main-event (aref key 0)))
     (cond
@@ -2427,6 +2444,14 @@ before the command is executed globally with terminated Isearch."
       ;; Swallow the up-event.
       (read-event)
       (setq this-command 'isearch-edit-string))
+     ;; Don't terminate the search for motion commands.
+     ((or (and (eq search-exit-option 'move)
+               (symbolp this-command)
+               (eq (get this-command 'isearch-move) t))
+          (and (eq search-exit-option 'shift-move)
+               this-command-keys-shift-translated))
+      (setq this-command-keys-shift-translated nil)
+      (setq isearch-pre-move-point (point)))
      ;; Other characters terminate the search and are then executed normally.
      (search-exit-option
       (isearch-done)
@@ -2436,13 +2461,28 @@ before the command is executed globally with terminated Isearch."
       (isearch-process-search-string key key)))))
 
 (defun isearch-post-command-hook ()
-  (when isearch-pre-scroll-point
+  (cond
+   (isearch-pre-scroll-point
     (let ((ab-bel (isearch-string-out-of-window isearch-pre-scroll-point)))
       (if ab-bel
 	  (isearch-back-into-window (eq ab-bel 'above) isearch-pre-scroll-point)
 	(goto-char isearch-pre-scroll-point)))
     (setq isearch-pre-scroll-point nil)
-    (isearch-update)))
+    (isearch-update))
+   ((memq search-exit-option '(move shift-move))
+    (when (and isearch-pre-move-point
+               (not (eq isearch-pre-move-point (point))))
+      (let ((string (buffer-substring-no-properties
+                     (or isearch-other-end isearch-opoint) (point))))
+        (if isearch-regexp (setq string (regexp-quote string)))
+        (setq isearch-string string)
+        (setq isearch-message (mapconcat 'isearch-text-char-description
+                                         string ""))
+        (setq isearch-yank-flag t)
+        (setq isearch-forward (<= (or isearch-other-end isearch-opoint) (point)))
+        (goto-char isearch-pre-move-point)
+        (isearch-search-and-update)))
+    (setq isearch-pre-move-point nil))))
 
 (defun isearch-quote-char (&optional count)
   "Quote special characters for incremental search.