Add refresh_many() method for batch handlers

docs/api/rattail/batch/handlers.rst

@@ -99,6 +99,8 @@
 
    .. automethod:: refresh
 
+   .. automethod:: refresh_many
+
    .. automethod:: refresh_row
 
    .. automethod:: locate_product_for_entry

rattail/batch/handlers.py

@@ -411,6 +411,27 @@ class BatchHandler(object):
         self.teardown_refresh(batch, progress=progress)
         return True
 
+    def refresh_many(self, batches, user=None, progress=None):
+        """
+        Refresh a set of batches, with given progress.  Default behavior is to
+        simply refresh each batch in succession.  Any batches which are already
+        executed are skipped.
+
+        Handlers may have to override this method if "grouping" or other
+        special behavior is needed.
+        """
+        needs_refresh = [batch for batch in batches
+                         if not batch.executed]
+        if not needs_refresh:
+            return
+
+        # TODO: should perhaps try to make the progress indicator reflect the
+        # "total" number of rows across all batches being refreshed?  seems
+        # like that might be more accurate, for the user.  but also harder.
+
+        for batch in needs_refresh:
+            self.do_refresh(batch, user, progress=progress)
+
     def refresh_row(self, row):
         """
         This method will be passed a row object which has already been properly