Submodule.Update, add Auth to SubmoduleUpdateOption, fixes #520

Author: mcuadros

options.go

@@ -194,6 +194,8 @@ type SubmoduleUpdateOptions struct {
 	// the current repository but also in any nested submodules inside those
 	// submodules (and so on). Until the SubmoduleRescursivity is reached.
 	RecurseSubmodules SubmoduleRescursivity
+	// Auth credentials, if required, to use with the remote repository.
+	Auth transport.AuthMethod
 }
 
 var (

submodule.go

@@ -218,7 +218,7 @@ func (s *Submodule) fetchAndCheckout(
 	ctx context.Context, r *Repository, o *SubmoduleUpdateOptions, hash plumbing.Hash,
 ) error {
 	if !o.NoFetch {
-		err := r.FetchContext(ctx, &FetchOptions{})
+		err := r.FetchContext(ctx, &FetchOptions{Auth: o.Auth})
 		if err != nil && err != NoErrAlreadyUpToDate {
 			return err
 		}