Digging Snow Layer yields one snow ball too much

If you dig up snow covers with a shovel, you should get a snowball. The bug is that you get two snowballs instead of one. Works with all shovels.

---

Further information provided by Orthotope:

Looking at the code, it seems to be a simple oversight. Previously, the thickness of snow was stored in its data value, using the range 0-7, so the number of snowballs dropped was (thickness + 1). With the transition to block states, the thickness is now internally represented as 1-8, but the formula for snowballs dropped wasn't changed, so it gives one extra.