X rebuild: tests: Inline _assertTrack

t.Helper() is relatively expensive

61s -> 58s

wcfs/internal/xbtree/path-reverse.patch

+To reduce allocs  -> no change in t
+diff --git a/wcfs/internal/xbtree/pptreesubset.go b/wcfs/internal/xbtree/pptreesubset.go
+index 43bd37e5..d8c15d9b 100644
+--- a/wcfs/internal/xbtree/pptreesubset.go
++++ b/wcfs/internal/xbtree/pptreesubset.go
+@@ -77,7 +77,7 @@ func (S PPTreeSubSet) Path(oid zodb.Oid) (path []zodb.Oid) {
+ 			panicf("node %s is not in the set  <- %v", oid, path)
+ 		}
+ 
+-		path = append([]zodb.Oid{oid}, path...)
++		path = append(path, oid) // in reverse
+ 		oid = t.parent
+ 
+ 		if oid == zodb.InvalidOid {
+@@ -85,6 +85,11 @@ func (S PPTreeSubSet) Path(oid zodb.Oid) (path []zodb.Oid) {
+ 		}
+ 	}
+ 
++	// we've built path in reverse order - revert it back
++	for i, j := 0, len(path)-1; i<j; i, j = i+1, j-1 {
++		path[i], path[j] = path[j], path[i]
++	}
++
+ 	return path
+ }
+ 

wcfs/internal/xbtree/pptreesubset-noptr.patch

+To reduce allocs  -> no change in t
+diff --git a/wcfs/internal/xbtree/pptreesubset.go b/wcfs/internal/xbtree/pptreesubset.go
+index 43bd37e5..b304a2d0 100644
+--- a/wcfs/internal/xbtree/pptreesubset.go
++++ b/wcfs/internal/xbtree/pptreesubset.go
+@@ -52,7 +52,7 @@ const debugPPSet = false
+ // Every node in the set comes with .parent pointer.
+ //
+ // XXX we only allow single parent/root case and report "tree corrupt" otherwise.
+-type PPTreeSubSet map[zodb.Oid]*nodeInTree
++type PPTreeSubSet map[zodb.Oid]nodeInTree // NOTE _not_ *nodeInTree to reduce preesure on GC
+ 
+ // nodeInTree represents tracking information about a node.
+ // XXX -> treeNode ?
+@@ -77,7 +77,7 @@ func (S PPTreeSubSet) Path(oid zodb.Oid) (path []zodb.Oid) {
+ 			panicf("node %s is not in the set  <- %v", oid, path)
+ 		}
+ 
+-		path = append([]zodb.Oid{oid}, path...)
++		path = append([]zodb.Oid{oid}, path...) // XXX less copy/alloc
+ 		oid = t.parent
+ 
+ 		if oid == zodb.InvalidOid {
+@@ -106,7 +106,6 @@ func (S PPTreeSubSet) AddPath(path []zodb.Oid) {
+ 
+ 	// go through path and add nodes to the set
+ 	parent := zodb.InvalidOid
+-	var pt *nodeInTree = nil
+ 	for _, oid := range path {
+ 		if oid == zodb.InvalidOid {
+ 			panicf("path has node with invalid oid: %v", path)
+@@ -114,7 +113,7 @@ func (S PPTreeSubSet) AddPath(path []zodb.Oid) {
+ 
+ 		t, already := S[oid]
+ 		if !already {
+-			t = &nodeInTree{parent: parent, nchild: 0}
++			t = nodeInTree{parent: parent, nchild: 0}
+ 			S[oid] = t
+ 		}
+ 		if t.parent != parent {
+@@ -123,12 +122,13 @@ func (S PPTreeSubSet) AddPath(path []zodb.Oid) {
+ 				oid, t.parent, parent)
+ 		}
+ 
+-		if pt != nil && !already {
++		if parent != zodb.InvalidOid && !already {
++			pt := S[parent]
+ 			pt.nchild++
++			S[parent] = pt
+ 		}
+ 
+ 		parent = oid
+-		pt = t
+ 	}
+ }
+ 
+@@ -226,7 +226,7 @@ func (A PPTreeSubSet) xUnionInplace(B PPTreeSubSet) {
+ 	for oid, t2 := range B {
+ 		t, already := A[oid]
+ 		if !already {
+-			t = &nodeInTree{parent: t2.parent, nchild: 0}
++			t = nodeInTree{parent: t2.parent, nchild: 0}
+ 			A[oid] = t
+ 			// remember to nchild++ in parent
+ 			if t.parent != zodb.InvalidOid {
+@@ -306,6 +306,7 @@ func (A PPTreeSubSet) xfixup(sign int, δnchild map[zodb.Oid]int) {
+ 	for oid, δnc := range δnchild {
+ 		t := A[oid] // t != nil as A is PP-connected
+ 		t.nchild += sign*δnc
++		A[oid] = t
+ 		if t.nchild == 0 {
+ 			gcq = append(gcq, oid)
+ 		}
+@@ -332,6 +333,7 @@ func (S PPTreeSubSet) gc1(oid zodb.Oid) {
+ 	for oid != zodb.InvalidOid {
+ 		t := S[oid]
+ 		t.nchild--
++		S[oid] = t
+ 		if t.nchild > 0 {
+ 			break
+ 		}
+@@ -398,7 +400,7 @@ func (S PPTreeSubSet) verify() {
+ func (orig PPTreeSubSet) Clone() PPTreeSubSet {
+ 	klon := make(PPTreeSubSet, len(orig))
+ 	for oid, t := range orig {
+-		klon[oid] = &nodeInTree{parent: t.parent, nchild: t.nchild}
++		klon[oid] = nodeInTree{parent: t.parent, nchild: t.nchild}
+ 	}
+ 	return klon
+ }
+diff --git a/wcfs/internal/xbtree/δbtail_test.go b/wcfs/internal/xbtree/δbtail_test.go
+index ad4b4a13..4d9b126d 100644
+--- a/wcfs/internal/xbtree/δbtail_test.go
++++ b/wcfs/internal/xbtree/δbtail_test.go
+@@ -359,7 +359,7 @@ func (rbs RBucketSet) _trackSetWithCov(tracked SetKey, outKeyCover *RangedKeySet
+ 		if kb.oid != zodb.InvalidOid {
+ 			track, already := trackSet[kb.oid]
+ 			if !already {
+-				track = &nodeInTree{parent: kb.parent.oid, nchild: 0}
++				track = nodeInTree{parent: kb.parent.oid, nchild: 0}
+ 				trackSet[kb.oid] = track
+ 				newNode = true
+ 			}
+@@ -378,7 +378,7 @@ func (rbs RBucketSet) _trackSetWithCov(tracked SetKey, outKeyCover *RangedKeySet
+ 			newParent := false
+ 			pt, already := trackSet[p.oid]
+ 			if !already {
+-				pt = &nodeInTree{parent: ppoid, nchild: 0}
++				pt = nodeInTree{parent: ppoid, nchild: 0}
+ 				trackSet[p.oid] = pt
+ 				newParent = true
+ 			}
+@@ -388,6 +388,7 @@ func (rbs RBucketSet) _trackSetWithCov(tracked SetKey, outKeyCover *RangedKeySet
+ 
+ 			if newNode {
+ 				pt.nchild++
++				trackSet[p.oid] = pt
+ 			}
+ 			newNode = newParent
+ 			p = p.parent

wcfs/internal/xbtree/δbtail_test.go

@@ -911,22 +911,14 @@ func xverifyΔBTail_Update1(t *testing.T, subj string, db *zodb.DB, treeRoot zod
 	}
 }
 
-// assertTrack verifies that trackSet == trackSetOK.
-// XXX place
-// XXX inline into δbtail.assertTrack?
-func _assertTrack(t *testing.T, subj string, trackSet, trackSetOK PPTreeSubSet) {
-	t.Helper()
-	if !trackSet.Equal(trackSetOK) {
-		t.Errorf("%s:\n\thave: %v\n\twant: %v", subj, trackSet, trackSetOK)
-	}
-}
-
 // assertTrack verifies state of .trackSet and ΔTtail.trackNew.
 // it assumes that only one tree root is being tracked.
 // XXX place
 func (δBtail *ΔBtail) assertTrack(t *testing.T, subj string, trackSetOK PPTreeSubSet, trackNewOK PPTreeSubSet) {
 	t.Helper()
-	_assertTrack(t, subj + ": trackSet", δBtail.trackSet, trackSetOK)
+	if !δBtail.trackSet.Equal(trackSetOK) {
+		t.Errorf("%s: trackSet:\n\thave: %v\n\twant: %v", subj, δBtail.trackSet, trackSetOK)
+	}
 
 	roots := SetOid{}
 	for root := range δBtail.vδTbyRoot {
@@ -958,7 +950,9 @@ func (δBtail *ΔBtail) assertTrack(t *testing.T, subj string, trackSetOK PPTree
 		t.Errorf("%s: trackNewRoots:\n\thave: %v\n\twant: %v", subj, δBtail.trackNewRoots, trackNewRootsOK)
 	}
 
-	_assertTrack(t, subj + ": vδT.trackNew", δTtail.trackNew, trackNewOK)
+	if !δTtail.trackNew.Equal(trackNewOK) {
+		t.Errorf("%s: vδT.trackNew:\n\thave: %v\n\twant: %v", subj, δTtail.trackNew, trackNewOK)
+	}
 }
 
 // xverifyΔBTail_rebuild verifies ΔBtail.rebuild during t0->t1->t2 transition.