`successfully` eats error output, which `git diff --check` provides when there are whitespace issues.

I'm not a huge fan of this implementation, but wasn't able to come up with another way to exit gracefully while providing the output I wanted.

To be honest, I didn't put too much effort into that, as my `vimrc` will strip all of the whitespace errors I run into on write, so I very rarely run into this.