Don't record unwalked references with the path resolver

Recording unwalked references with the path resolver means that the
footnote for an extreme object might use an unwalked references in the
"names" for the object, even though the object must necessarily also
be reachable from at least one reference that _was_ walked. Fix this
by not recording unwalked references with the path resolver.

Author: mhagger

sizes/graph.go

@@ -43,6 +43,7 @@ type RefGrouper interface {
 
 type refSeen struct {
 	git.Reference
+	walked bool
 	groups []RefGroupSymbol
 }
 
@@ -102,6 +103,7 @@ func ScanRepositoryUsingGraph(
 				refsSeen,
 				refSeen{
 					Reference: ref,
+					walked:    walk,
 					groups:    groups,
 				},
 			)
@@ -372,7 +374,7 @@ func ScanRepositoryUsingGraph(
 	progressMeter.Start("Processing references: %d")
 	for _, refSeen := range refsSeen {
 		progressMeter.Inc()
-		graph.RegisterReference(refSeen.Reference, refSeen.groups)
+		graph.RegisterReference(refSeen.Reference, refSeen.walked, refSeen.groups)
 	}
 	progressMeter.Done()
 
@@ -428,15 +430,17 @@ func NewGraph(rg RefGrouper, nameStyle NameStyle) *Graph {
 	}
 }
 
-func (g *Graph) RegisterReference(ref git.Reference, groups []RefGroupSymbol) {
+func (g *Graph) RegisterReference(ref git.Reference, walked bool, groups []RefGroupSymbol) {
 	g.historyLock.Lock()
 	g.historySize.recordReference(g, ref)
 	for _, group := range groups {
 		g.historySize.recordReferenceGroup(g, group)
 	}
 	g.historyLock.Unlock()
 
-	g.pathResolver.RecordReference(ref)
+	if walked {
+		g.pathResolver.RecordReference(ref)
+	}
 }
 
 func (g *Graph) HistorySize() HistorySize {