to felt or not?

I would suggest a house wrap. You don't want that felt to become a vapor barrier when you don't have a proper one on the inside.

What about an uninsulated attached garage? I have to replace the clapboard siding this summer. It has nothing under the siding now (the house is wrapped).

I would use house wrap because it will let water vapor out but not let water in. Suffering from OCD I would also spend the time to overlap and tape it per the recommendations. Before I put it up I would make sure I caulked every nook and cranny with the highest quality caulk I could afford. Then I would caulk the hardie per recommendations. Don't forget the flashing on the butt joints.

Suffer once and get paid back for years.

Colbyt

I have not really done that, but I think I would use neither unless you lived in a very windy area. I would guess that either could be used.