Use a vendor directory for repeatable builds - fixes #816

This is using godep to manage the vendor directory.

vendor/google.golang.org/appengine/internal/transaction.go

@@ -0,0 +1,30 @@
+package internal
+
+// This file implements hooks for applying datastore transactions.
+
+import (
+	"reflect"
+
+	"github.com/golang/protobuf/proto"
+
+	pb "google.golang.org/appengine/internal/datastore"
+)
+
+var transactionSetters = make(map[reflect.Type]reflect.Value)
+
+// RegisterTransactionSetter registers a function that sets transaction information
+// in a protocol buffer message. f should be a function with two arguments,
+// the first being a protocol buffer type, and the second being *datastore.Transaction.
+func RegisterTransactionSetter(f interface{}) {
+	v := reflect.ValueOf(f)
+	transactionSetters[v.Type().In(0)] = v
+}
+
+// ApplyTransaction applies the transaction t to message pb
+// by using the relevant setter passed to RegisterTransactionSetter.
+func ApplyTransaction(pb proto.Message, t *pb.Transaction) {
+	v := reflect.ValueOf(pb)
+	if f, ok := transactionSetters[v.Type()]; ok {
+		f.Call([]reflect.Value{v, reflect.ValueOf(t)})
+	}
+}