Fix the usage

Author: dgutov

diff-hl.el

@@ -1293,11 +1293,10 @@ The value of this variable is a mode line template as in
         ;; instead, but only when they don't call `revert-buffer':
         (add-hook 'magit-not-reverted-hook 'diff-hl-update nil t)
         (add-hook 'text-scale-mode-hook 'diff-hl-maybe-redefine-bitmaps nil t)
-        (when-let* ((rev (cl-find-if
-                          (lambda (pair)
-                            (when (string-prefix-p (car pair) default-directory)
-                              (cdr pair)))
-                          diff-hl-reference-revision-projects-cache)))
+        (when-let* ((rev (cdr
+                          (cl-find-if
+                           (lambda (pair) (string-prefix-p (car pair) default-directory))
+                           diff-hl-reference-revision-projects-cache))))
           (setq-local diff-hl-reference-revision rev)))
     (remove-hook 'after-save-hook 'diff-hl-update t)
     (remove-hook 'after-change-functions 'diff-hl-edit t)