Context is not passed when updating submodules

[onee-only]

When pulling or cloning from a repo, go-git will update submodules if the option is set.

The problem is when calling (*Worktree).updateSubmodules. It doesn't take the context from a caller.

go-git/worktree.go

Lines 151 to 158 in c7feada

	func (w *Worktree) updateSubmodules(o *SubmoduleUpdateOptions) error {
	s, err := w.Submodules()
	if err != nil {
	return err
	}
	o.Init = true
	return s.Update(o)
	}

It creates new context internally.

go-git/submodule.go

Lines 298 to 301 in c7feada

	// Update updates all the submodules in this list.
	func (s Submodules) Update(o *SubmoduleUpdateOptions) error {
	return s.UpdateContext(context.Background(), o)
	}

This can lead to situations where we can't gracefully handle slow fetching of submodules or etc.

Is there any reason that it ignores context from caller?
If there isn't, I think we better pass context to the funciton.