barrels, rolling, and gravity

Barrels roll. It is a fact that, outside of Minecraft, barrels roll. I propose a way to make this happen in Minecraft as well. When right-clicked with a shovel, Minecraft barrels would roll one block horizontally to the direction it was placed, then be affected by gravity, becoming a "rolling block" rather than a falling block. A rolling block retains its directional placement, and won't break (or stop) when it hits incomplete blocks (such as stairs, paths, or flowers)  It will not roll anywhere if placed vertically, (though it would still fall) and would roll horizontally to the direction it faces, rolling down stairs and across path blocks and slabs until it cannot roll any further.

Other blocks that could be rolled (with a shovel) are logs, stripped logs, and maybe pillars.