Unify layered provenance history

metadata.go

@@ -1,7 +1,7 @@
 package configkit
 
-// Metadata provides detached presence, origin, and history queries for a load.
-// Its zero value contains no paths.
+// Metadata provides detached effective presence/origin and chronological history
+// queries for a load. Its zero value contains no paths.
 type Metadata struct {
 	fields  map[string]FieldInfo
 	history map[string][]Change
@@ -27,8 +27,10 @@ func (m Metadata) IsExplicit(path Path) bool {
 	return ok && info.Explicit
 }
 
-// History returns detached definition and resolution records for path. Unknown and
-// invalid paths return nil.
+// History returns detached definition and resolution records for path. A record's
+// Path can be an ancestor when that container operation replaced or removed path.
+// Removed historical paths can have history even though Lookup returns false.
+// Unknown and invalid paths return nil.
 func (m Metadata) History(path Path) []Change {
 	if !path.valid() {
 		return nil