X maintain per-root holeIdx

Else in case of two files used simultaneously the index is messed up.
Fixes test_wcfs_watch_2files and now all wcfs tests pass again.

wcfs/δbtail.go

@@ -174,11 +174,10 @@ type ΔBtail struct {
 	// tracked nodes index: node -> parent + accessed holes under this node	XXX -> holeIdx
 	// we only allow single parent/root case and report "tree corrupt" otherwise.
 	// trackIdx describes @head state
-	//trackIdx map[zodb.Oid]nodeTrack
 	trackIdx trackIndex
 
-	// XXX tracked holes
-	holeIdx treeSetKey
+	// XXX root -> tracked holes
+	holeIdxByRoot map[zodb.Oid]treeSetKey
 
 //	// tracked objects that are not yet taken into account in current δBtail
 //	trackNew SetOid
@@ -355,7 +354,7 @@ func NewΔBtail(at0 zodb.Tid, db *zodb.DB) *ΔBtail {
 		δZtail:        zodb.NewΔTail(at0),
 		byRoot:        map[zodb.Oid]*ΔTtail{},
 		trackIdx:      trackIndex{},
-		holeIdx:  treeSetKey{SetKey{}},
+		holeIdxByRoot: map[zodb.Oid]treeSetKey{},
 		db:       db,
 	}
 }
@@ -402,8 +401,9 @@ func (δBtail *ΔBtail) Track(key Key, keyPresent bool, path []Node) error { //
 	// track is track of path[-1]  (i.e. leaf)
 
 	// remember missing keys in track of leaf node (bucket or top-level ø tree)
+	holeIdx := δBtail.holeIdxFor(root)
 	if !keyPresent {
-		δBtail.holeIdx.Add(key)
+		holeIdx.Add(key)
 		//track.holes.Add(key)
 	} else {
 		/*
@@ -411,7 +411,7 @@ func (δBtail *ΔBtail) Track(key Key, keyPresent bool, path []Node) error { //
 			panicf("[%v] was previously requested to be tracked as ø", key)
 		}
 		*/
-		if δBtail.holeIdx.Has(key) {
+		if holeIdx.Has(key) {
 			panicf("[%v] was previously requested to be tracked as ø", key)
 		}
 	}
@@ -426,6 +426,15 @@ func (δBtail *ΔBtail) Track(key Key, keyPresent bool, path []Node) error { //
 	return nil
 }
 
+func (δBtail *ΔBtail) holeIdxFor(root zodb.Oid) treeSetKey {
+	holeIdx, ok := δBtail.holeIdxByRoot[root]
+	if !ok {
+			holeIdx = treeSetKey{SetKey{}}
+			δBtail.holeIdxByRoot[root] = holeIdx
+	}
+	return holeIdx
+}
+
 // XXX place
 // XXX doc
 func (tidx trackIndex) AddNodePath(path []Node) { // XXX Tree|Bucket; path[0] = root
@@ -504,7 +513,7 @@ func (δBtail *ΔBtail) Update(δZ *zodb.EventCommit) (_ ΔB, err error) {
 
 	tracef("Update δZ: %v\n", δZ.Changev)
 	tracef("trackIdx:       %v\n", δBtail.trackIdx)
-	tracef("holeIdx:   %v\n", δBtail.holeIdx)
+	tracef("holeIdxByRoot:  %v\n", δBtail.holeIdxByRoot)
 
 	δZTC, δtopsByRoot := δBtail.δZConnectTracked(δZ)
 
@@ -529,7 +538,8 @@ func (δBtail *ΔBtail) Update(δZ *zodb.EventCommit) (_ ΔB, err error) {
 	}
 
 	for root, δtops := range δtopsByRoot {
-		δT, err := treediff(ctx, root, δtops, δZTC, δBtail.trackIdx, δBtail.holeIdx, zconnOld, zconnNew)
+		holeIdx := δBtail.holeIdxByRoot[root]
+		δT, err := treediff(ctx, root, δtops, δZTC, δBtail.trackIdx, holeIdx, zconnOld, zconnNew)
 		if err != nil {
 			return ΔB{}, err
 		}

wcfs/δbtail_test.go

@@ -678,8 +678,9 @@ func xverifyΔBTail1(t *testing.T, subj string, db *zodb.DB, treeRoot zodb.Oid,
 	// verify δbtail.holeIdx  against @at1
 	// holes1 = tracked1 \ kv1
 	holes1 := xkv1.holeIdx(initialTrackedKeys)
-	if !reflect.DeepEqual(holes1, δbtail.holeIdx.SetKey) {
-		badf("δbtail.holeIdx1 wrong  ; holeIdx=%v  holeIdxOK=%v", δbtail.holeIdx, holes1)
+	holeIdx := δbtail.holeIdxFor(treeRoot)
+	if !reflect.DeepEqual(holes1, holeIdx.SetKey) {
+		badf("δbtail.holeIdx1 wrong  ; holeIdx=%v  holeIdxOK=%v", holeIdx, holes1)
 	}
 
 	// verify δbtail.trackIdx against @at1
@@ -700,8 +701,8 @@ func xverifyΔBTail1(t *testing.T, subj string, db *zodb.DB, treeRoot zodb.Oid,
 	// verify δbtail.holeIdx  against @at2
 	// holes2 = tracked2 \ kv2  ( = kadj[tracked1] \ kv2)
 	holes2 := xkv2.holeIdx(kadjTracked)
-	if !reflect.DeepEqual(holes2, δbtail.holeIdx.SetKey) {
-		badf("δbtail.holeIdx2 wrong  ; holeIdx=%v  holeIdxOK=%v", δbtail.holeIdx, holes2)
+	if !reflect.DeepEqual(holes2, holeIdx.SetKey) {
+		badf("δbtail.holeIdx2 wrong  ; holeIdx=%v  holeIdxOK=%v", holeIdx, holes2)
 	}
 
 	// verify δbtail.trackIdx  against @at2