feat(default): narrow to multi-line region in +default/search-buffer

Since multi-line inputs are useless to consult-line and swiper, I've
changed +default/search-buffer to be more DWIM (do-what-I-mean). i.e. if
a selection is active when invoking it, and...

- The selection is multi-line: restrict the search to that region.
- The selection is *not* multi-line: use the selection as the initial
  input.
- Otherwise, search the whole buffer as normal.

modules/config/default/autoload/search.el

@@ -24,25 +24,37 @@ If prefix ARG is set, prompt for a directory to search from."
 ;;;###autoload
 (defun +default/search-buffer ()
   "Conduct a text search on the current buffer.
-If a selection is active, pre-fill the prompt with it."
+
+If a selection is active and multi-line, perform a search restricted to that
+region.
+
+If a selection is active and not multi-line, use the selection as the initial
+input and search the whole buffer for it."
   (interactive)
-  (cond ((or (featurep! :completion helm)
+  (let (start end multiline-p)
-             (featurep! :completion ivy))
+    (save-restriction
-         (call-interactively
+      (when (region-active-p)
-          (if (region-active-p)
+        (setq start (region-beginning)
-              #'swiper-isearch-thing-at-point
+              end   (region-end)
-            #'swiper-isearch)))
+              multiline-p (/= (line-number-at-pos start)
-        ((featurep! :completion vertico)
+                              (line-number-at-pos end)))
-         (if (region-active-p)
+        (deactivate-mark)
-             (let ((start (region-beginning))
+        (when multiline-p
-                   (end   (region-end)))
+          (narrow-to-region start end)))
-               (deactivate-mark)
+      (cond ((or (featurep! :completion helm)
-               (consult-line
+                 (featurep! :completion ivy))
-                (replace-regexp-in-string
+             (call-interactively
-                 " " "\\\\ "
+              (if (and start end (not multiline-p))
-                 (rxt-quote-pcre
+                  #'swiper-isearch-thing-at-point
-                  (buffer-substring-no-properties start end)))))
+                #'swiper-isearch)))
-           (call-interactively #'consult-line)))))
+            ((featurep! :completion vertico)
+             (if (and start end (not multiline-p))
+                 (consult-line
+                  (replace-regexp-in-string
+                   " " "\\\\ "
+                   (rxt-quote-pcre
+                    (buffer-substring-no-properties start end))))
+               (call-interactively #'consult-line)))))))
 
 ;;;###autoload
 (defun +default/search-project (&optional arg)