> Imagine I have never used Emacs before.
    > However I have been using vi exclusively for 15 years. I have a passing familiarity with Emacs bindings from working shells, but they are an exercise in misery.
    > 
    > So I want to change Emacs to use Evil.

Why Evil? I don't understand this conclusion; Evil is intended for Vim emulation rather than Vi. Emacs comes with Viper mode out of the box. It's well documented, implements all of Vi and Ex commands, and can be turned on with a simple `M-x viper-mode`; no configuration or external packages needed.

Similarly for Git, Emacs comes with VC built in: It's well documented and provides a powerful uniform interface across a number of VC "backends", including Git.