Ask HN: Do you keep a personal knowledge repository?

And if so, which software do you use? I'm fascinated by storing things that I learn outside of my own brain. Ideally I'd love to create my own mini intranet of information, basically a personal wiki, that I can go to first before having to Google things, especially for my field of study.

I've looked into various Wiki packages but none quite seem to offer what I'm looking for (Mac, no need for a webserver, cross device functionality, math markup, searchability, tags)

If you do keep a personal knowledge repository, can you please describe your workflow for using and maintaining one for all the new knowledge you acquire?