org-e-confluence: Add asynchronous export support

* contrib/lisp/org-e-confluence.el (org-e-confluence-export-as-confluence):
  Add asynchronous export support.

contrib/lisp/org-e-confluence.el

@@ -140,7 +140,7 @@
 
 ;; main interactive entrypoint
 (defun org-e-confluence-export-as-confluence
-  (&optional subtreep visible-only body-only ext-plist)
+  (&optional async subtreep visible-only body-only ext-plist)
   "Export current buffer to a text buffer.
 
 If narrowing is active in the current buffer, only export its
@@ -148,6 +148,10 @@ narrowed part.
 
 If a region is active, export that region.
 
+A non-nil optional argument ASYNC means the process should happen
+asynchronously.  The resulting buffer should be accessible
+through the `org-export-stack' interface.
+
 When optional argument SUBTREEP is non-nil, export the sub-tree
 at point, extracting information from the headline properties
 first.
@@ -166,11 +170,22 @@ Export is done in a buffer named \"*Org E-Confluence Export*\", which
 will be displayed when `org-export-show-temporary-export-buffer'
 is non-nil."
   (interactive)
-  (let ((outbuf (org-export-to-buffer
-		 'e-confluence "*Org E-Confluence Export*"
-		 subtreep visible-only body-only ext-plist)))
-    (with-current-buffer outbuf (text-mode))
-    (when org-export-show-temporary-export-buffer
-      (switch-to-buffer-other-window outbuf))))
+  (if async
+      (org-export-async-start
+	  (lambda (output)
+	    (with-current-buffer (get-buffer-create "*Org E-Confluence Export*")
+	      (erase-buffer)
+	      (insert output)
+	      (goto-char (point-min))
+	      (text-mode)
+	      (org-export-add-to-stack (current-buffer) 'e-confluence)))
+	`(org-export-as 'e-confluence ,subtreep ,visible-only ,body-only
+			',ext-plist))
+    (let ((outbuf (org-export-to-buffer
+		   'e-confluence "*Org E-Confluence Export*"
+		   subtreep visible-only body-only ext-plist)))
+      (with-current-buffer outbuf (text-mode))
+      (when org-export-show-temporary-export-buffer
+	(switch-to-buffer-other-window outbuf)))))
 
 (provide 'org-e-confluence)