I would encourage you not to split things up too finely. A single repo for your environment would allow you to see all related changes with git. E.g. if you set up a new VM it might need a playbook to set something up, a script to automate a task, and a DNS entry. With a well put together commit message explaining why you're making those changes there's not much need for external documentation.
Maybe if you want some more info organised in a wiki, point to the initial commit where you introduced some set up. That way you can see how something was structured. Or if you have a issue tracker you can comment with research on something and then close the issue when you commit a resolution.
Try not to have info spread out too much or maintaining all the pieces will become a chore. Make it simple and easy to keep up.