emacs: Factor out synchronous notmuch JSON invocations

Previously this code was duplicated between show and reply.  This
factors out synchronously invoking notmuch and parsing the output as
JSON.

emacs/notmuch-lib.el

@@ -371,6 +371,20 @@ contents of ERR-FILE will be included in the error message."
     ;; Mimic `process-lines'
     (error "%s exited with status %s" (car command) exit-status))))
 
+(defun notmuch-call-notmuch-json (&rest args)
+  "Invoke `notmuch-command' with `args' and return the parsed JSON output.
+
+The returned output will represent objects using property lists
+and arrays as lists."
+
+  (with-temp-buffer
+    (apply #'call-process notmuch-command nil (list t nil) nil args)
+    (goto-char (point-min))
+    (let ((json-object-type 'plist)
+	  (json-array-type 'list)
+	  (json-false 'nil))
+      (json-read))))
+
 ;; Compatibility functions for versions of emacs before emacs 23.
 ;;
 ;; Both functions here were copied from emacs 23 with the following copyright:

emacs/notmuch-mua.el

@@ -158,13 +158,7 @@ list."
     (setq args (append args (list query-string)))
 
     ;; Get the reply object as JSON, and parse it into an elisp object.
-    (with-temp-buffer
-      (apply 'call-process (append (list notmuch-command nil (list t nil) nil) args))
-      (goto-char (point-min))
-      (let ((json-object-type 'plist)
-	    (json-array-type 'list)
-	    (json-false 'nil))
-	(setq reply (json-read))))
+    (setq reply (apply #'notmuch-call-notmuch-json args))
 
     ;; Extract the original message to simplify the following code.
     (setq original (plist-get reply :original))

emacs/notmuch-query.el

@@ -29,18 +29,11 @@ A thread is a forest or list of trees. A tree is a two element
 list where the first element is a message, and the second element
 is a possibly empty forest of replies.
 "
-  (let  ((args '("show" "--format=json"))
-	 (json-object-type 'plist)
-	 (json-array-type 'list)
-	 (json-false 'nil))
+  (let ((args '("show" "--format=json")))
     (if notmuch-show-process-crypto
 	(setq args (append args '("--decrypt"))))
     (setq args (append args search-terms))
-    (with-temp-buffer
-      (progn
-	(apply 'call-process (append (list notmuch-command nil (list t nil) nil) args))
-	(goto-char (point-min))
-	(json-read)))))
+    (apply #'notmuch-call-notmuch-json args)))
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; Mapping functions across collections of messages.