Add oneoff_import() helper method to MasterView class

tailbone/views/master.py

@@ -1622,6 +1622,30 @@ class MasterView(View):
                 progress.session['success_url'] = self.get_index_url()
                 progress.session.save()
 
+    def oneoff_import(self, importer, host_object=None):
+        """
+        Basic helper method, to do a one-off import (or export, depending on
+        perspective) of the "current instance" object.  Where the data "goes"
+        depends on the importer you provide.
+        """
+        if not host_object:
+            host_object = self.get_instance()
+
+        host_data = importer.normalize_host_object(host_object)
+        if not host_data:
+            return
+
+        key = importer.get_key(host_data)
+        local_object = importer.get_local_object(key)
+        if local_object:
+            if importer.allow_update:
+                local_data = importer.normalize_local_object(local_object)
+                if importer.data_diffs(local_data, host_data) and importer.allow_update:
+                    local_object = importer.update_object(local_object, host_data, local_data)
+            return local_object
+        elif importer.allow_create:
+            return importer.create_object(key, host_data)
+
     def execute(self):
         """
         Execute an object.