trie: update merkle hash when stage is commited

trie/node.go

@@ -17,6 +17,7 @@ func newNode(val Value) *node {
 // We clear the Merkle Hash for every node along the path, including the root.
 // Calculation of the hash happens much less frequently then updating to the MerkleTrie.
 func update(n *node, key Key, val Value) {
+	n.hash = nil
 	// Follow the path to reach the node.
 	for _, k := range key {
 		if n.links[k] == nil {

trie/stage.go

@@ -39,6 +39,9 @@ func (s *Stage) Update(key Key, val Value) error {
 
 // Commit ...
 func (s *Stage) Commit(head *Commit, meta CommitMeta) (*Commit, error) {
+	// Update Merkle Hash.
+	s.MerkleHash()
+
 	c := NewCommit(head, meta, s.MerkleTrie)
 
 	s.MerkleTrie = New()