.

wcfs/internal/xbtree/δbtail.go

@@ -513,7 +513,8 @@ func (δBtail *ΔBtail) Update(δZ *zodb.EventCommit) (_ ΔB, err error) {
 		// δtkeycov1 != ø   ->  rebuild δTtail
 		if !δT1.δtkeycov1.Empty() && δBtail.δZtail.Len() > 1 {
 			//δTtail.trackNew = ... // ~δtkeycov1
-			δTtail.trackNew = nil // XXX stub
+			//δTtail.trackNew = nil // XXX stub
+			δTtail.trackNew = δT1.δtrack.XXXδtkeycovSet() // ~δtkeycov1  XXX correct?
 
 			// XXX vvv we can skip computing diff for HEAD~..HEAD (we just
 			//     computed it in _Update1)