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

Just because I came here looking for a one-time solution (in my case, I usually use vim but this one time I wanted to use VS Code) for a single command and others might want to know as well:

GIT_EDITOR='code -w' git rebase -i …

Here's my git/hub version just for context:

git version 2.24.2 (Apple Git-127)
hub version 2.14.1