.

wcfs/δbtail.go

@@ -465,6 +465,7 @@ func treediff(ctx context.Context, root zodb.Oid, δZT SetOid, trackIdx map[zodb
 		// XXX no - not needed here - keys cannot migrate in between two disconnected subtrees
 		// DEL k -> Tkextra += k
 		// +k    -> Tkextra -= k
+		fmt.Printf("-> δtop: %v\n", δtop)
 		for k,δv := range δtop {
 			δT[k] = δv
 		}
@@ -647,6 +648,7 @@ func diffT(ctx context.Context, a, b *Tree, δZTC SetOid, trackIdx map[zodb.Oid]
 				δv.New = δv1.New
 			}
 
+			fmt.Printf("    [%v] merge %s %s  -> %s\n", k, δv1, δv2, δv)
 			if δv.Old != δv.New {
 				δ[k] = δv
 			} else {

wcfs/δbtail_test.go

@@ -1141,3 +1141,15 @@ func sortedKeys(kv map[Key]Δstring) []Key {
 	})
 	return keyv
 }
+
+// String is like default %v, but uses ø for VDEL.
+func (δv ΔValue) String() string {
+	old, new := DEL, DEL
+	if δv.Old != VDEL {
+		old = δv.Old.String()
+	}
+	if δv.New != VDEL {
+		new = δv.New.String()
+	}
+	return fmt.Sprintf("{%s %s}", old, new)
+}