Add: get git submodules in one step

--recursive
--recurse-submodules
After the clone is created, initialize all submodules within, using their default settings. This is equivalent to running git submodule update --init --recursive immediately after the clone is finished. This option is ignored if the cloned repository does not have a worktree/checkout (i.e. if any of --no-checkout/-n, --bare, or --mirror is given)

from http://git-scm.com/docs/git-clone

pkg/build/repo/repo.go

@@ -94,10 +94,10 @@ func (r *Repo) Commands() []string {
 	branch := r.Branch
 	if len(branch) == 0 {
 		branch = "master"
-	}
+	}r
 
 	cmds := []string{}
-	cmds = append(cmds, fmt.Sprintf("git clone --branch=%s %s %s", branch, r.Path, r.Dir))
+	cmds = append(cmds, fmt.Sprintf("git clone --recursive --branch=%s %s %s", branch, r.Path, r.Dir))
 
 	switch {
 	// if a specific commit is provided then we'll