Add a TODO comment for UnsafeDetectSchemaVersion on how to simplify t…

…he implementation

Signed-off-by: Benjamin Wang <[email protected]>

server/storage/schema/schema.go

@@ -95,6 +95,12 @@ func UnsafeDetectSchemaVersion(lg *zap.Logger, tx backend.UnsafeReader) (v semve
 	if vp != nil {
 		return *vp, nil
 	}
+
+	// TODO: remove the operations of reading the fields `confState`
+	// and `term` in 3.7. We only need to be back-compatible
+	// with 3.6 when we are running 3.7, and the `storageVersion`
+	// already exists in all versions >= 3.6, so we don't need to
+	// use any other fields to identify the etcd's storage version.
 	confstate := UnsafeConfStateFromBackend(lg, tx)
 	if confstate == nil {
 		return v, fmt.Errorf("missing confstate information")