* unified the action / attachment handling

- mu4e-utils.el: s/mu4e-offer-action/mu4e-choose-action/, and return a
    function now, rather than executing it directly
  - mu4e-view.el: implement the attachment handling function in terms of
    mu4e-choose-action, and each other. also fix some small issues.

emacs/mu4e-utils.el

@@ -392,18 +392,18 @@ there is no message at point."
   "Get FIELD (a symbol, see `mu4e-header-names') for the message at
 point in eiter the headers buffer or the view buffer."
   (plist-get (mu4e-message-at-point t) field))
-
+
 (defun mu4e-choose-action (prompt actions)
   "Ask user with PROMPT to choose some action from ACTIONS. ACTIONS
-is a list of actions like `mu4e-view-attachments-actions',
-`mu4e-view-actions', `mu4e-header-actions'. Then, call the function
+is a list of actions like `mu4e-view-attachments-actions',
+`mu4e-view-actions', `mu4e-header-actions'. Returns the
 action (function) to invoke, or nil. "
   (if (null actions)
-    (message "No actions of this type defined")
-    (let ((kar (mu4e-read-option prompt actions)))
-      (dolist (action actions)
-	(let ((shortcut (cadr action)) (func (nth 2 action)))
-	  (when (eq kar shortcut)
+    (message "No actions of this type defined")
+    (let* ((kar (mu4e-read-option prompt actions))
+	    (action ;; find the action for this kar
+	      (find-if (lambda (ac) (eq kar (cadr ac))) actions)))
+      (when action
 	(nth 2 action))))) ;; return func
 
 (defun mu4e-capture-message ()