For a presentation I was holding at work I created a git commit timeline that could help me “cheat a little bit” as Ingrid Espelid Hovig would’ve put it.
However, I needed to go back in time and put something at the beginning of that commit timeline.

So - doing a commit between commit A and commit B:

1. Start an interactive rebase to a commit at some point before the commit you want to insert after: git rebase -i <commithash>
2. Vim should start up and you’ll get a list of commits. Find the commit you want to add after and switch from pick to edit
3. Save and exit vim
4. Make the changes you want and do: git add and git commit
5. Continue the rebase: git rebase --continue

Obviously the hardest part of this is step 3…