you die
Punch it or strike it with a sword, just like with any other mob. However, pigs do not drop porkchops when they die as of version 0.3.2 alpha.
u die & that's it
Ellen Craft died in 1891.
Juanita Craft died in 1985.
Just keep hitting it with any item, even your hand, and it will eventually die. However, if you would like to hasten the process, use a tool such as a sword and the sheep will die quicker.
You need to trust your craft. If something fails, you could die. Miscalculate something, caflook.
Marcella Craft died on 1959-12-12.
Molly Craft died on 1978-10-25.
Harry Craft died on 1995-08-03.
Die by the Drop was created in 2009-12.
Lucy Craft Laney died on 1933-10-24.