I only realized very recently that being able to specify .gitignore files in any part of a repo can be combined with wildcards to just put `.gitignore` with `*` in a arbitrary directories to make them get ignored without needing to modify any wider configuration.

This has the disadvantage though, that this user level gitignore file will not be in the repo, which means that other less careful contributors have to fix ignoribg for themselves.

And then you have a known path to script up all your repos' stuff for backup

yes, but user level is not a repo level