Fix argument to `replace-match'

* hydra.el (hydra--format): Update.

* hydra-test.el (hydra-format-3): Add test.

Fixes #91

hydra-test.el

@@ -740,6 +740,17 @@ _f_ auto-fill-mode:    %`auto-fill-function
                 ("q" nil "" :cmd-name bar/nil))))
            '(concat (format "  bar %s\n" foo) "{a}, [q]"))))
 
+(ert-deftest hydra-format-3 ()
+  (should (equal
+           (let ((hydra-fontify-head-function
+                  'hydra-fontify-head-greyscale))
+             (hydra--format
+              'bar
+              nil
+              "\n_<SPC>_   ^^ace jump\n"
+              '(("<SPC>" ace-jump-char-mode nil :cmd-name bar/ace-jump-char-mode))))
+           '(concat (format "%s   ace jump\n" "{<SPC>}") ""))))
+
 (ert-deftest hydra-format-with-sexp-1 ()
   (should (equal
            (let ((hydra-fontify-head-function

hydra.el

@@ -491,7 +491,7 @@ The expressions can be auto-expanded according to NAME."
                             (or
                              hydra-key-format-spec
                              (concat "%" (match-string 3 docstring) "s"))
-                            nil nil docstring)))
+                            t nil docstring)))
                  (error "Unrecognized key: _%s_" key))))
 
             (t