util: add migration stub

pkg/util/migration_stub.go

@@ -0,0 +1,26 @@
+// Copyright 2017 The Cockroach Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+// implied. See the License for the specific language governing
+// permissions and limitations under the License.
+
+package util
+
+import "github.com/cockroachdb/cockroach/pkg/util/envutil"
+
+var _ = IsMigrated()
+
+// IsMigrated gives a crude way of landing changes that need a migration until
+// #16977 is implemented. When IsMigrated() returns false (the default),
+// mixed-cluster compatibility with 1.0 is required.
+func IsMigrated() bool {
+	return envutil.EnvOrDefaultBool("COCKROACH_MIGRATED", false)
+}