How do I make Git use the editor of my choice for commits?

Question

I would prefer to write my commit messages in Vim, but it is opening them in Emacs.

How do I configure Git to always use Vim? Note that I want to do this globally,

Answer 1

For Windows users who want to use neovim with the Windows Subsystem for Linux:

git config core.editor "C:/Windows/system32/bash.exe --login -c 'nvim .git/COMMIT_EDITMSG'"

This is not a fool-proof solution as it doesn't handle interactive rebasing (for example). Improvements very welcome!