Caesar's Writings on the Gallic War

The boundaries that he lays out actually what become Provence is because it's divided up of Gaul. He gives us a definition of it and this has an impact on the way we think of the Gallic Wars as being written. Caesar maps out what he's going to conquer. What are the margins of the territory then that he's defined as this? Where does he intend to go? Some people think he got to the end and just wrote it all together. There are scholarly arguments about whether the style changes therefore it was probably written year by year.