Use empty dir when importing git submodules.

git/git.go

@@ -3,7 +3,6 @@ package git
 
 import (
 	"context"
-	"errors"
 	"io/ioutil"
 	"path"
 	"path/filepath"
@@ -16,6 +15,7 @@ import (
 	"github.com/ipfs/go-cid"
 	ipld "github.com/ipfs/go-ipld-format"
 	"github.com/ipfs/go-merkledag"
+	ufs "github.com/ipfs/go-unixfs"
 	ufsio "github.com/ipfs/go-unixfs/io"
 	"github.com/multiverse-vcs/go-multiverse/data"
 	"github.com/multiverse-vcs/go-multiverse/unixfs"
@@ -217,7 +217,7 @@ func (i *importer) AddTreeEntry(entry object.TreeEntry) (ipld.Node, error) {
 	case filemode.Dir:
 		return i.AddTree(entry.Hash)
 	case filemode.Submodule:
-		return nil, errors.New("submodules not supported")
+		return ufs.EmptyDirNode(), nil
 	}
 
 	blob, err := i.repo.BlobObject(entry.Hash)

git/git_test.go

@@ -41,7 +41,7 @@ func TestImportFromFS(t *testing.T) {
 	defer os.RemoveAll(dir)
 
 	opts := git.CloneOptions{
-		URL: "https://github.com/multiverse-vcs/go-multiverse",
+		URL: "https://github.com/hsoft/collapseos",
 	}
 
 	_, err = git.PlainClone(dir, false, &opts)
@@ -62,4 +62,4 @@ func TestImportFromFS(t *testing.T) {
 	if repo.Name != "test" {
 		t.Error("unexpected repo name")
 	}
-}
+}