refactor(core): init DAG and its dependents in shared constructor

fix: remove merkledag import

may need to squash this commit into the merkledag move commit

core/core.go

@@ -96,6 +96,17 @@ func NewIPFSNode(ctx context.Context, option ConfigOption) (*IpfsNode, error) {
 	if err != nil {
 		return nil, err
 	}
+
+	// Need to make sure it's perfectly clear 1) which variables are expected
+	// to be initialized at this point, and 2) which variables will be
+	// initialized after this point.
+
+	node.DAG = merkledag.NewDAGService(node.Blocks)
+	node.Pinning, err = pin.LoadPinner(node.Datastore, node.DAG)
+	if err != nil {
+		node.Pinning = pin.NewPinner(node.Datastore, node.DAG)
+	}
+	node.Resolver = &path.Resolver{DAG: node.DAG}
 	return node, nil
 }
 
@@ -161,13 +172,6 @@ func Standard(cfg *config.Config, online bool) ConfigOption {
 			return nil, debugerror.Wrap(err)
 		}
 
-		n.DAG = merkledag.NewDAGService(n.Blocks)
-		n.Pinning, err = pin.LoadPinner(n.Datastore, n.DAG)
-		if err != nil {
-			n.Pinning = pin.NewPinner(n.Datastore, n.DAG)
-		}
-		n.Resolver = &path.Resolver{DAG: n.DAG}
-
 		success = true
 		return n, nil
 	}

test/epictest/core.go

@@ -10,7 +10,6 @@ import (
 	core "github.com/jbenet/go-ipfs/core"
 	bitswap "github.com/jbenet/go-ipfs/exchange/bitswap"
 	bsnet "github.com/jbenet/go-ipfs/exchange/bitswap/network"
-	merkledag "github.com/jbenet/go-ipfs/merkledag"
 	host "github.com/jbenet/go-ipfs/p2p/host"
 	peer "github.com/jbenet/go-ipfs/p2p/peer"
 	dht "github.com/jbenet/go-ipfs/routing/dht"
@@ -47,7 +46,6 @@ func MocknetTestRepo(p peer.ID, h host.Host, conf testutil.LatencyConfig) core.C
 			Exchange:   exch,
 			Datastore:  ds,
 			PeerHost:   h,
-			DAG:        merkledag.NewDAGService(blockservice),
 			Blocks:     blockservice,
 			Routing:    dhtt,
 			Identity:   p,