Sadly, the bad part is git's user interface. It hides the pretty parts underneath. There is a concept of "the next commit" or, equivalently, "the pending comm

Sadly, the bad part is git's user interface. It hides the pretty parts underneath. There is a concept of "the next commit" or, equivalently, "the pending commit". In the documentation, this gets called "indexed" or "cached" or "staged" --- three different names! And if you want to diff with it, you can't refer to it by name. You need to use an option, so it's "git diff --cached <other commit>. I know git's internals, mostly because it lets me navigate its bad user interface.