mu4e: allow to disable the global mode-line items

Fixes #2463

mu4e/mu4e-modeline.el

@@ -48,6 +48,14 @@ display the bookmark name rather than the query."
   :type 'boolean
   :group 'mu4e-modeline)
 
+(defcustom mu4e-modeline-show-global t
+  "Whether to populate global modeline segments.
+
+If non-nil, show both buffer-specific and global modeline items,
+otherwise only present buffer-specific information."
+  :type 'boolean
+  :group 'mu4e-modeline)
+
 (defvar-local mu4e--modeline-buffer-items nil
   "List of buffer-local items for the mu4e modeline.
 Each element is function that evaluates to a string.")
@@ -90,15 +98,17 @@ originate.")
             (mapconcat
              (lambda (func) (or (funcall func) "")) lst " ")))
          (global-string ;; global string is _cached_ as it may be expensive.
-          (or mu4e--modeline-global-string-cached
-              (setq mu4e--modeline-global-string-cached
-                    (funcall collect mu4e--modeline-global-items)))))
+          (and
+           mu4e-modeline-show-global
+           (or mu4e--modeline-global-string-cached
+               (setq mu4e--modeline-global-string-cached
+                     (funcall collect mu4e--modeline-global-items))))))
     (concat
      ;; (local) buffer items are _not_ cached, so they'll get update
      ;; automatically when leaving the buffer.
      (mu4e--modeline-quote-and-truncate
       (funcall collect mu4e--modeline-buffer-items))
-     " "
+     (and global-string " ")
      global-string)))
 
 (define-minor-mode mu4e-modeline-mode

mu4e/mu4e.texi

@@ -3127,8 +3127,11 @@ To completely turn off the modeline support, set @code{mu4e-modeline-support} to
 @item global: information about the results for the ``favorite query''
 @end itemize
 
-All of the bookmark items provide more details in their @code{help-echo}, i.e.,
-their tooltip.
+The global indicators can be disabled by setting @code{mu4e-modeline-show-global}
+to @t{nil}.
+
+All of the bookmark items provide more details in their @code{help-echo},
+i.e., their tooltip.
 
 @subsection Query parameters bookmark item
 The query parameters in the modeline start with the various query flags (such as