Support nil value for notmuch-poll-script to run "notmuch new" instead of
an external script, and make this the new default. "notmuch new" is run
using the configured notmuch-command.

This allows taking better advantage of the "notmuch new" hooks from emacs
without intermediate scripts.

Signed-off-by: Jani Nikula <jani@nikula.org>

---

v3: only documentation changes suggested by Austin and Dmitry.
---
 emacs/notmuch.el |   35 +++++++++++++++++++++++++----------
 1 files changed, 25 insertions(+), 10 deletions(-)

diff --git a/emacs/notmuch.el b/emacs/notmuch.el
index 8936149..675a110 100644
--- a/emacs/notmuch.el
+++ b/emacs/notmuch.el
@@ -965,28 +965,43 @@ same relative position within the new buffer."
     (notmuch-search query oldest-first target-thread target-line continuation)
     (goto-char (point-min))))
 
-(defcustom notmuch-poll-script ""
+(defcustom notmuch-poll-script nil
   "An external script to incorporate new mail into the notmuch database.
 
-If this variable is non empty, then it should name a script to be
-invoked by `notmuch-search-poll-and-refresh-view' and
+This variable controls the action invoked by
+`notmuch-search-poll-and-refresh-view' and
 `notmuch-hello-poll-and-update' (each have a default keybinding
-of 'G'). The script could do any of the following depending on
+of 'G') to incorporate new mail into the notmuch database.
+
+If set to nil (the default), new mail is processed by invoking
+\"notmuch new\". Otherwise, this should be set to a string that
+gives the name of an external script that processes new mail. If
+set to the empty string, no command will be run.
+
+The external script could do any of the following depending on
 the user's needs:
 
 1. Invoke a program to transfer mail to the local mail store
 2. Invoke \"notmuch new\" to incorporate the new mail
-3. Invoke one or more \"notmuch tag\" commands to classify the mail"
-  :type 'string
+3. Invoke one or more \"notmuch tag\" commands to classify the mail
+
+Note that the recommended way of achieving the same is using
+\"notmuch new\" hooks."
+  :type '(choice (const :tag "notmuch new" nil)
+		 (const :tag "Disabled" "")
+		 (string :tag "Custom script"))
   :group 'notmuch)
 
 (defun notmuch-poll ()
-  "Run external script to import mail.
+  "Run \"notmuch new\" or an external script to import mail.
 
-Invokes `notmuch-poll-script' if it is not set to an empty string."
+Invokes `notmuch-poll-script', \"notmuch new\", or does nothing
+depending on the value of `notmuch-poll-script'."
   (interactive)
-  (if (not (string= notmuch-poll-script ""))
-      (call-process notmuch-poll-script nil nil)))
+  (if (stringp notmuch-poll-script)
+      (if (not (string= notmuch-poll-script ""))
+	  (call-process notmuch-poll-script nil nil))
+    (call-process notmuch-command nil nil nil "new")))
 
 (defun notmuch-search-poll-and-refresh-view ()
   "Invoke `notmuch-poll' to import mail, then refresh the current view."
-- 
1.7.5.4