X wcfs/xbtree: Fix update not to add duplicate extra point if rebuild -...

X wcfs/xbtree: Fix update not to add duplicate extra point if rebuild  - called by Update - already added it

It was failing e.g. as

=== RUN   TestΔBTail/rebuild/T4/T1,3-T/T-T-T-T/B0:b-B1:c,2:j-T-B4:d/B3:h→T/T2,3/T-T-T/B1:d-B2:c-B3:i/_T{3};R/_→T2/B1:g-B2:c,3:i
    δbtail_test.go:917: after Update(@at1→@at2): vδT:
        have:
        	@at1: map[0:{b ø} 1:{c d} 2:{j c} 3:{h i} 4:{d ø}]
        	@at2: map[1:{d g}]
        vδb/root:
        	@at1
        	@at2
        	@at2	<-- HERE

wcfs/internal/xbtree/δbtail.go

@@ -607,12 +607,10 @@ func (δBtail *ΔBtail) Update(δZ *zodb.EventCommit) (_ ΔB, err error) {
 		// XXX rebuild lastRevOf
 	}
 
-	// vδBroots += δB
-	δroots := setOid{}
+	// vδBroots += δB  (δB.Rev could be already there added by ^^^ rebuild)
 	for root := range δB.ΔByRoot {
-		δroots.Add(root)
+		δBtail.vδBroots_Update1(root, δB.Rev)
 	}
-	δBtail.vδBroots = append(δBtail.vδBroots, _ΔBroots{Rev: δB.Rev, ΔRoots: δroots})
 
 	return δB, err
 }
@@ -699,22 +697,26 @@ func (δBtail *ΔBtail) _Update1(δZ *zodb.EventCommit) (δB1 _ΔBUpdate1, err e
 func (δBtail *ΔBtail) vδBroots_Update(root zodb.Oid, δrevSet setTid) {
 	// XXX locking
 	for rev := range δrevSet {
-		l := len(δBtail.vδBroots)
-		j := sort.Search(l, func(k int) bool {
-			return rev <= δBtail.vδBroots[k].Rev
-		})
-		if j == l || δBtail.vδBroots[j].Rev != rev {
-			δBroots := _ΔBroots{Rev: rev, ΔRoots: setOid{}}
-			// insert(@j, δBroots)
-			δBtail.vδBroots = append(δBtail.vδBroots[:j],
-						 append([]_ΔBroots{δBroots},
-						 δBtail.vδBroots[j:]...)...)
-		}
-		δBroots := δBtail.vδBroots[j]
-		δBroots.ΔRoots.Add(root)
+		δBtail.vδBroots_Update1(root, rev)
 	}
 }
 
+func (δBtail *ΔBtail) vδBroots_Update1(root zodb.Oid, rev zodb.Tid) {
+	l := len(δBtail.vδBroots)
+	j := sort.Search(l, func(k int) bool {
+		return rev <= δBtail.vδBroots[k].Rev
+	})
+	if j == l || rev != δBtail.vδBroots[j].Rev {
+		δBroots := _ΔBroots{Rev: rev, ΔRoots: setOid{}}
+		// insert(@j, δBroots)
+		δBtail.vδBroots = append(δBtail.vδBroots[:j],
+					 append([]_ΔBroots{δBroots},
+					 δBtail.vδBroots[j:]...)...)
+	}
+	δBroots := δBtail.vδBroots[j]
+	δBroots.ΔRoots.Add(root)
+}
+
 // ForgetPast forgets history entries with revision ≤ revCut.
 func (δBtail *ΔBtail) ForgetPast(revCut zodb.Tid) {
 	// XXX locking

wcfs/internal/xbtree/δbtail_test.go

@@ -388,7 +388,7 @@ func TestΔBTail(t *testing.T) {
 			  99: K(3,99,oo),
 			  oo: K(3,99,oo)}),
 
-		// XXX wrong rebuild
+		// Update adds extra dup point to vδBroots
 		"T4/T1,3-T/T-T-T-T/B0:b-B1:c,2:j-T-B4:d/B3:h",
 		"T/T2,3/T-T-T/B1:d-B2:c-B3:i",
 		"T2/B1:g-B2:c,3:i",