Add GetNoTxn to txnBuf as a hack.

filter/txnBuf/context.go

Index: filter/txnBuf/context.go
diff --git a/filter/txnBuf/context.go b/filter/txnBuf/context.go
index b044328820e4a32b1c987f72c0e554b63831e732..63e1cace82b81b63833ffe9208bca19b031892d7 100644
--- a/filter/txnBuf/context.go
+++ b/filter/txnBuf/context.go
@@ -45,3 +45,17 @@ func memoryCorruption(err error) {
 		panic(err)
 	}
 }
+
+// GetNoTxn allows you to to escape the buffered transaction (if any), and get
+// a non-transactional handle to the datastore. This does not invalidate the
+// currently-buffered transaction, but it also does not see any effects of it.
+//
+// TODO(iannucci): This is messy, but mostly because the way that transactions
+// work is messy. Fixing luci/gae#issues/23 would help though, because it means
+// we could make transactionality recorded by a single index in the context
+// instead of relying on function nesting.
+func GetNoTxn(c context.Context) ds.Interface {
+	c = context.WithValue(c, dsTxnBufParent, nil)
+	c = context.WithValue(c, dsTxnBufHaveLock, nil)
+	return ds.GetNoTxn(c)
+}