mu4e: improve update data

Update doccount after indexing.

mu4e/mu4e-server.el

@@ -385,7 +385,10 @@ The server output is as follows:
          ((plist-get sexp :info)
           (funcall mu4e-info-func sexp))
 
-         ;; get some data
+         ;; get some data XXX generalize
+         ((plist-get sexp :doccount)
+          (plist-put mu4e--server-props :doccount
+                     (mu4e--server-plist-get sexp :doccount)))
          ((plist-get sexp :maildirs)
           (setq mu4e-maildir-list (mu4e--server-plist-get sexp :maildirs)))
 
@@ -556,9 +559,16 @@ get at most MAX contacts."
 
 (defun mu4e--server-data (kind)
   "Request data of some KIND.
-KIND is a symbol. Currently supported kinds: maildirs."
-  (mu4e--server-call-mu
-   `(data :kind ,kind)))
+KIND is a symbol or a list of symbols. Currently supported kinds:
+ `maildirs', `doccount'."
+  (pcase kind
+    ((pred (lambda (k) (memq k '(maildirs doccount))))
+     (mu4e--server-call-mu `(data :kind ,kind)))
+    ((pred listp)
+     (when kind
+       (mu4e--server-data (car kind))
+       (mu4e--server-data (cdr kind))))
+    (_ (mu4e-error "Unexpected kind %s" kind))))
 
 (defun mu4e--server-find (query threads sortfield sortdir maxnum skip-dups
                                 include-related)