don't return CIDs on add

The caller can just call `node.Cid()` and returning CIDs from `AddMany` requires
allocation.

batch.go

@@ -71,7 +71,7 @@ func (t *Batch) asyncCommit() {
 		}
 	}
 	go func(b []Node) {
-		_, err := t.ds.AddMany(b)
+		err := t.ds.AddMany(b)
 		t.commitResults <- err
 	}(t.nodes)
 

batch_test.go

@@ -41,24 +41,20 @@ func (d *testDag) GetMany(ctx context.Context, cids []*cid.Cid) <-chan *NodeOpti
 	return out
 }
 
-func (d *testDag) Add(node Node) (*cid.Cid, error) {
+func (d *testDag) Add(node Node) error {
 	d.mu.Lock()
 	defer d.mu.Unlock()
-	c := node.Cid()
-	d.nodes[c.KeyString()] = node
-	return c, nil
+	d.nodes[node.Cid().KeyString()] = node
+	return nil
 }
 
-func (d *testDag) AddMany(nodes []Node) ([]*cid.Cid, error) {
+func (d *testDag) AddMany(nodes []Node) error {
 	d.mu.Lock()
 	defer d.mu.Unlock()
-	cids := make([]*cid.Cid, len(nodes))
-	for i, n := range nodes {
-		c := n.Cid()
-		d.nodes[c.KeyString()] = n
-		cids[i] = c
+	for _, n := range nodes {
+		d.nodes[n.Cid().KeyString()] = n
 	}
-	return cids, nil
+	return nil
 }
 
 func (d *testDag) Remove(c *cid.Cid) error {

merkledag.go

@@ -43,7 +43,7 @@ type DAGService interface {
 	NodeGetter
 
 	// Add adds a node to this DAG.
-	Add(Node) (*cid.Cid, error)
+	Add(Node) error
 
 	// Remove removes a node from this DAG.
 	//
@@ -54,5 +54,5 @@ type DAGService interface {
 	//
 	// Consider using NewBatch instead of calling this directly if you need
 	// to add an unbounded number of nodes to avoid buffering too much.
-	AddMany([]Node) ([]*cid.Cid, error)
+	AddMany([]Node) error
 }