Project incoming source destinations through tier operations

internal/engine/overlay.go

@@ -65,13 +65,28 @@ func (a *assemblyAccumulator) applyOverlayWithCollectionPolicy(
 	sequencePolicy sequencePolicy,
 	declarations []sequenceDeclarationSpec,
 ) []Diagnostic {
+	_, diagnostics := a.applyOverlayWithCollectionProjection(overlay, incomingOrigins, incomingPolicies, applications, layer, sequencePolicy, declarations)
+	return diagnostics
+}
+
+// applyOverlayWithCollectionProjection also returns the incoming tier's item
+// assignments so acquisition evidence can follow the same operation as values.
+func (a *assemblyAccumulator) applyOverlayWithCollectionProjection(
+	overlay *document.Node,
+	incomingOrigins map[string]Origin,
+	incomingPolicies collectionPolicyScope,
+	applications []historyApplication,
+	layer Layer,
+	sequencePolicy sequencePolicy,
+	declarations []sequenceDeclarationSpec,
+) ([]sequenceHistoryContribution, []Diagnostic) {
 	if a == nil || a.current == nil || a.current.root == nil || a.current.root.Kind != document.Mapping || overlay == nil || overlay.Kind != document.Mapping {
-		return invalidOverlayDocument()
+		return nil, invalidOverlayDocument()
 	}
 	mergeOriginContribution(a.current.origins, Path{}, incomingOrigin(incomingOrigins, Path{}, overlay, layer))
 	sequences, diagnostics := mergeOverlayMappingsWithCollectionPolicy(a, overlay, incomingOrigins, incomingPolicies, layer, sequencePolicy, declarations)
 	if len(diagnostics) != 0 {
-		return diagnostics
+		return nil, diagnostics
 	}
 	if len(applications) == 0 {
 		application := historyApplication{layer: layer, value: overlay, sequences: sequences}
@@ -83,7 +98,7 @@ func (a *assemblyAccumulator) applyOverlayWithCollectionPolicy(
 			a.current.applications = append(a.current.applications, application)
 		}
 	}
-	return nil
+	return sequences, nil
 }
 
 func mergeOverlayMappingsWithCollectionPolicy(