* mu4e: automatically update headers when there are updates during indexing,

while there is no current user-interaction. Document this, add to NEWS

  (set `mu4e-headers-auto-update' to nil) to disable

NEWS

@@ -21,6 +21,8 @@
       `mu4e-user-mail-address-list'
     - support tags (i.e.., X-Keywords and friends) in the headers-view, and the
       message view. Thanks to Abdó Roig-Maranges. New field ":tags".
+    - automatically update the headers buffer when new messages are found during
+      indexing; set `mu4e-headers-auto-update' to nil to disable this.
 
 * Old news
   :PROPERTIES:

mu4e/mu4e-headers.el

@@ -84,6 +84,12 @@ vertical split-view."
   :type 'integer
   :group 'mu4e-headers)
 
+(defcustom mu4e-headers-auto-update t
+  "Whether to automatically update the current headers buffer if an
+indexing operation showed changes."
+  :type 'boolean
+  :group 'mu4e-headers)
+
 
 ;; marks for headers of the form; each is a cons-cell (basic . fancy)
 ;; each of which is basic ascii char and something fancy, respectively
@@ -643,6 +649,16 @@ after the end of the search results."
   (make-local-variable 'global-mode-string)
   (set (make-local-variable 'hl-line-face) 'mu4e-header-highlight-face)
 
+  ;; maybe update the current headers upon indexing changes
+  (add-hook 'mu4e-index-updated-hook
+    (defun mu4e~headers-auto-update ()
+      "Update the current headers buffer after indexing has brought
+some changes, `mu4e-headers-auto-update' is non-nil and there is no
+user-interaction ongoing."
+      (when (and mu4e-headers-auto-update (not (active-minibuffer-window)))
+	(with-current-buffer mu4e~headers-buffer
+	  (mu4e-headers-rerun-search)))) nil t)
+
   (setq
     truncate-lines t
     buffer-undo-list t ;; don't record undo information

mu4e/mu4e.texi

@@ -733,6 +733,10 @@ u=@emph{unread}. The tooltip for this field also contains this information.
 @item The subject field also indicates the discussion threads @footnote{using
 Jamie Zawinski's mail threading algorithm,
 @url{http://www.jwz.org/doc/threading.html}}.
+@item The headers view is @emph{automatically updated} if any changes are
+found during the indexing process, and if there is not current
+user-interaction. If you do not want such automatic updates, set
+@code{mu4e-headers-auto-update} to @code{nil}.
 @end itemize
 
 @node Keybindings
@@ -2791,6 +2795,9 @@ some soundfile, change as needed):
   (defun new-mail-sound ()
     (shell-command "aplay ~/Sounds/boing.wav&")))
 @end lisp
+@item @emph{It seems my headers-buffer is automatically updated when new
+  messages are found during the indexing process -- can I disable this
+  somehow?} Yes - set @code{mu4e-headers-auto-update} to @code{nil}.
 @item @emph{I don't use @t{offlineimap}, @t{fetchmail} etc., I get my mail
 through my own mailserver. What should I use for
 @code{mu4e-get-mail-command}}? Use @t{"true"} (or don't do anything, it's the