Initial implementation of an elasticsearch indexer in Go

Closes #1 (closed)

git/repo.go

@@ -5,6 +5,7 @@ import (
 	"gopkg.in/src-d/go-git.v4"
 	"gopkg.in/src-d/go-git.v4/plumbing"
+	"gopkg.in/src-d/go-git.v4/plumbing/filemode"
 	"gopkg.in/src-d/go-git.v4/plumbing/object"
 	"gopkg.in/src-d/go-git.v4/utils/merkletrie"
 )
@@ -95,6 +96,12 @@ func (r *Repo) EachFileChange(ins, mod, del FileFunc) error {
 	}
 	for _, change := range changes {
+		// FIXME(nick): submodules may need better support
+		// https://github.com/src-d/go-git/issues/317
+		if change.From.TreeEntry.Mode == filemode.Submodule || change.To.TreeEntry.Mode == filemode.Submodule {
+			continue
+		}
+
 		fromF, toF, err := change.Files()
 		if err != nil {
 			return err