How to enable code folding in editor as default

[avanc]

Fold sections in the editor is a helpful feature. Is there a way to activate it as default (i.e. everything is folded instead of unfolded)?
I found 01a6582 but there is nothing mentioned regarding a config parameter.

[yagebu]

AFAICT, there's no built-in configuration for codemirror for this. So this would probably have to be some effect that runs on file switches in the editor. A PR implementing this would be welcome.