Allow for the "%s`foo" spec.

* hydra.el (hydra--format): Update. Treat variables in the same way as
  s-expressions.

* hydra-test.el (hydra-format-2): Add test.
(hydra-format-with-sexp-2): Add test.

Fixes #85

hydra-test.el

@@ -705,7 +705,7 @@ The body can be accessed via `hydra-vi/body'."
        ("l" text-scale-decrease "out")
        ("q" nil "quit"))))))
 
-(ert-deftest hydra-format ()
+(ert-deftest hydra-format-1 ()
   (should (equal
            (let ((hydra-fontify-head-function
                   'hydra-fontify-head-greyscale))
@@ -728,7 +728,19 @@ _f_ auto-fill-mode:    %`auto-fill-function
 %s auto-fill-mode:    %S
 " "{a}" abbrev-mode "{d}" debug-on-error "{f}" auto-fill-function) "[[q]]: quit"))))
 
-(ert-deftest hydra-format-with-sexp ()
+(ert-deftest hydra-format-2 ()
+  (should (equal
+           (let ((hydra-fontify-head-function
+                  'hydra-fontify-head-greyscale))
+             (hydra--format
+              'bar
+              nil
+              "\n  bar %s`foo\n"
+              '(("a" (quote t) "" :cmd-name bar/lambda-a)
+                ("q" nil "" :cmd-name bar/nil))))
+           '(concat (format "  bar %s\n" foo) "{a}, [q]"))))
+
+(ert-deftest hydra-format-with-sexp-1 ()
   (should (equal
            (let ((hydra-fontify-head-function
                   'hydra-fontify-head-greyscale))
@@ -743,6 +755,21 @@ _f_ auto-fill-mode:    %`auto-fill-function
                        (buffer-narrowed-p)))
              "[[q]]: cancel"))))
 
+(ert-deftest hydra-format-with-sexp-2 ()
+  (should (equal
+           (let ((hydra-fontify-head-function
+                  'hydra-fontify-head-greyscale))
+             (hydra--format
+              'hydra-toggle nil
+              "\n_n_ narrow-or-widen-dwim %s(progn (message \"checking\")(buffer-narrowed-p))asdf\n"
+              '(("n" narrow-to-region nil) ("q" nil "cancel"))))
+           '(concat (format "%s narrow-or-widen-dwim %sasdf\n"
+                     "{n}"
+                     (progn
+                       (message "checking")
+                       (buffer-narrowed-p)))
+             "[[q]]: cancel"))))
+
 (ert-deftest hydra-compat-colors-1 ()
   (should (equal (hydra--head-color
                   '("e" (message "Exiting now") "blue")

hydra.el

@@ -466,14 +466,13 @@ HEAD's binding is returned as a string wrapped with [] or {}."
   (funcall (or hydra-fontify-head-function 'hydra-fontify-head-default)
            head body))
 
-(defun hydra--format (name body docstring heads)
+(defun hydra--format (_name body docstring heads)
   "Generate a `format' statement from STR.
 \"%`...\" expressions are extracted into \"%S\".
 NAME, BODY, DOCSTRING and HEADS are parameters of `defhydra'.
 The expressions can be auto-expanded according to NAME."
   (setq docstring (replace-regexp-in-string "\\^" "" docstring))
   (let ((rest (hydra--hint body heads))
-        (prefix (symbol-name name))
         (start 0)
         varlist
         offset)
@@ -495,22 +494,14 @@ The expressions can be auto-expanded according to NAME."
                             nil nil docstring)))
                  (error "Unrecognized key: _%s_" key))))
 
-            ((eq ?` (aref (match-string 2 docstring) 0))
-             (push (hydra--unalias-var
-                    (substring (match-string 2 docstring) 1) prefix)
-                   varlist)
-             (setq docstring
-                   (replace-match
-                    (concat "%" (match-string 1 docstring) "S")
-                    nil nil docstring 0)))
-
             (t
-             (let* ((spec (match-string 1 docstring))
-                    (lspec (length spec))
-                    (me2 (match-end 2)))
+             (let* ((varp (if (eq ?` (aref (match-string 2 docstring) 0)) 1 0))
+                    (spec (match-string 1 docstring))
+                    (lspec (length spec)))
                (setq offset
                      (with-temp-buffer
-                       (insert (substring docstring (+ 1 start (length spec))))
+                       (insert (substring docstring (+ 1 start varp
+                                                       (length spec))))
                        (goto-char (point-min))
                        (push (read (current-buffer)) varlist)
                        (- (point) (point-min))))
@@ -521,7 +512,7 @@ The expressions can be auto-expanded according to NAME."
                      (concat
                       (substring docstring 0 start)
                       "%" spec
-                      (substring docstring (+ me2 offset -1))))))))
+                      (substring docstring (+ start offset 1 lspec varp))))))))
     (if (eq ?\n (aref docstring 0))
         `(concat (format ,(substring docstring 1) ,@(nreverse varlist))
                  ,rest)