mu4e-mark: add confirmation for mu4e-mark-unmark-all

Fixes #1234

mu4e/mu4e-mark.el

@@ -385,7 +385,7 @@ work well.
 If NO-CONFIRMATION is non-nil, don't ask user for confirmation."
   (interactive "P")
   (mu4e--mark-in-context
-   (let* ((marknum (hash-table-count mu4e--mark-map))
+   (let* ((marknum (mu4e-mark-marks-num))
           (prompt (format "Are you sure you want to execute %d mark%s?"
                           marknum (if (> marknum 1) "s" ""))))
      (if (zerop marknum)
@@ -409,15 +409,19 @@ If NO-CONFIRMATION is non-nil, don't ask user for confirmation."
                              docid msg target))
                 (mu4e-error "Unrecognized mark %S" mark))))
           mu4e--mark-map))
-       (mu4e-mark-unmark-all)
+       (mu4e-mark-unmark-all 'no-confirm)
        (message nil)))))
 
-(defun mu4e-mark-unmark-all ()
+(defun mu4e-mark-unmark-all (&optional no-confirmation)
   "Unmark all marked messages."
   (interactive)
   (mu4e--mark-in-context
-   (when (or (null mu4e--mark-map) (zerop (hash-table-count mu4e--mark-map)))
+   (when (zerop (mu4e-mark-marks-num))
      (mu4e-warn "Nothing is marked"))
+   (let* ((marknum (hash-table-count mu4e--mark-map))
+          (prompt (format "Are you sure you want to unmark %d message%s?"
+                          marknum (if (> marknum 1) "s" ""))))
+     (when (or no-confirmation (y-or-n-p prompt))
        (maphash
         (lambda (docid _val)
           (save-excursion
@@ -425,13 +429,12 @@ If NO-CONFIRMATION is non-nil, don't ask user for confirmation."
               (mu4e-mark-set 'unmark))))
         mu4e--mark-map)
        ;; in any case, clear the marks map
-   (mu4e--mark-clear)))
+       (mu4e--mark-clear)))))
 
 (defun mu4e-mark-docid-marked-p (docid)
   "Is the given DOCID marked?"
   (when (gethash docid mu4e--mark-map) t))
 
-
 (defun mu4e-mark-marks-num ()
   "Return the number of mark-instances in the current buffer."
   (mu4e--mark-in-context