.

wcfs/δbtail.go

@@ -301,7 +301,11 @@ func (δ *δtrackIndex) Update(δ2 *δtrackIndex) {
 	}
 }
 
-// XXX Revert
+// Reverse changes δ=diff(A->B) to δ'=diff(A<-B).
+func (δ *δtrackIndex) Reverse() {
+	δ.Del, δ.Add = δ.Add, δ.Del
+	// δnchildNonLeafs stays the same
+}
 
 
 // gc1 garbage-collects oid and cleans up its parent down-up.