emacs: Re-arrange message sending code

Define a new `mail-user-agent' (`notmuch-user-agent') and use it by
default. Re-arrange various routines that send mail to use this
(compose, reply, forward). Insert a `User-Agent:' header by default.

This is the real commit for this functionality this time. The
previous attempt to merge this code:

	commit 57926bc7b0f784cbacb620fda0ee5157e2e0ff27

was botched (by Carl Worth, not David) to include only the Makefile
change. So the build was broken until this commit that actually adds
the new file.

1 files changed, 16 insertions, 0 deletions

diff --git a/emacs/notmuch-lib.el b/emacs/notmuch-lib.el
index 274d7ec5..47c74b9e 100644
--- a/emacs/notmuch-lib.el
+++ b/emacs/notmuch-lib.el
@@ -33,6 +33,22 @@
   :type '(alist :key-type (string) :value-type (string))
   :group 'notmuch)
 
+;;
+
+(defun notmuch-version ()
+  "Return a string with the notmuch version number."
+  (let ((long-string
+	 ;; Trim off the trailing newline.
+	 (substring (shell-command-to-string
+		     (concat notmuch-command " --version"))
+		    0 -1)))
+    (if (string-match "^notmuch\\( version\\)? \\(.*\\)$"
+		      long-string)
+	(match-string 2 long-string)
+      "unknown")))
+
+;;
+
 ;; XXX: This should be a generic function in emacs somewhere, not
 ;; here.
 (defun point-invisible-p ()