Cheat Sheet: misguiding usage of 'index' to describe 'git diff --staged'

Problem to solve

The cheat sheet describes 'git diff --staged' as showing the difference between 'staging area' and 'index', the last one being described as 'repository committed status'. As far as I know, this is not the usual meaning of 'index'.

Further details

Technically, as far as I know, the index is a git internal (file based) structure to track different kind of changes. From my experience, the words 'index' and 'staging area' are used synonymous in many documentations.

The git book on https://git-scm.com/book/en/v1/Getting-Started-Git-Basics supports this view: "It’s sometimes referred to as the index, but it’s becoming standard to refer to it as the staging area."

Proposal

Documentation of 'git diff --staged' should be something like: 'show changes between staging area and the latest commit'