Allow to use minor-mode-maps and more

* hydra.el (hydra-create): Add a third optional argument. When it's not
  supplied, the behavior should remain the same. Otherwise, it's a
  lambda that's used instead of `global-set-key', with the same semantics.

* README.md: Update.

re #1

README.md

@@ -26,3 +26,32 @@ You can expand the examples in-place, it still looks elegant:
 See the [introductory blog post](http://oremacs.com/2015/01/20/introducing-hydra/) for more information.
 
 ![hydra](http://oremacs.com/download/Hydra.png)
+
+## Using Hydra to define bindings other than global ones
+
+You can use the third optional argument of `hydra-create` for this (it defaults to `global-set-key`).
+Here's an example:
+
+```cl
+(hydra-create "z"
+  '(("l" . forward-char)
+    ("h" . backward-char)
+    ("j" . next-line)
+    ("k" . previous-line))
+  (lambda (key command)
+    (define-key lispy-mode-map key command)))
+```
+
+For this simple case, there's even a shortcut: if you give a keymap as the third argument,
+the lambda will be generated for you:
+
+```cl
+(hydra-create "z"
+  '(("l" . forward-char)
+    ("h" . backward-char)
+    ("j" . next-line)
+    ("k" . previous-line))
+    lispy-mode-map)
+```
+
+

hydra.el

@@ -51,15 +51,21 @@
 (require 'cl-lib)
 
 ;;;###autoload
-(defmacro hydra-create (body heads)
-  "Create a hydra with a BODY prefix and HEADS.
+(defmacro hydra-create (body heads &optional method)
+  "Create a hydra with a BODY prefix and HEADS with METHOD.
 This will result in `global-set-key' statements with the keys
 being the concatenation of BODY and each head in HEADS.  HEADS is
 an alist of (KEY . FUNCTION).
 
 After one of the HEADS is called via BODY+KEY, it and the other
 HEADS can be called with only KEY (no need for BODY).  This state
-is broken once any key binding that is not in HEADS is called."
+is broken once any key binding that is not in HEADS is called.
+
+METHOD is a lambda takes two arguments: a KEY and a COMMAND.
+It defaults to `global-set-key'.
+When `(keymapp METHOD)`, it becomes:
+
+    (lambda (key command) (define-key METHOD key command))"
   (declare (indent 1))
   (let* ((keymap (make-sparse-keymap))
          (heads (eval heads))
@@ -67,9 +73,17 @@ is broken once any key binding that is not in HEADS is called."
                  (lambda (x)
                    (define-key keymap (car x)
                      (intern (format "hydra-%s-%S" body (cdr x)))))
-                 heads)))
+                 heads))
+         (method (cond ((null method)
+                        'global-set-key)
+
+                       ((keymapp (eval method))
+                        `(lambda (key command) (define-key ,method key command)))
+
+                       (t
+                        method))))
     `(progn
-       (global-set-key ,(kbd body) nil)
+       (,method ,(kbd body) nil)
        ,@(cl-mapcar
           (lambda (head name)
             `(defun ,name ()
@@ -91,7 +105,7 @@ Call the head: `%S'."
           heads names)
        ,@(cl-mapcar
           (lambda (head name)
-            `(global-set-key ,(kbd (concat body " " (car head))) #',name))
+            `(,method ,(kbd (concat body " " (car head))) #',name))
           heads names))))
 
 (provide 'hydra)