TiddlyWiki might be a good option. Technically it’s a wiki, but it is a single HTML page with all functionality built in JavaScript, you could host it on GH pages, though you wouldn’t be able to use its save feature there (you would have to save to your local machine and the deploy a new version). It stores text in little (or large) cards which can be given a title, tags and other metadata, and it providesa full search system.
It saves into the tiddlywiki HTML file. The default behaviour is to then trigger the browser to download the file. You can absolutely store it in a git repository.