Cool idea. I was confused why I didn't see the compound file after selecting multiple RuleSets, until I realized I needed to click the "preview" button.

Would love to see this as a cli tool: I always have to Google "github python gitignore" > raw > copy > pbpaste.

Thanks. Now that I see it, it actually is a bit confusing, I'll add an about section or at least some UI cues.

I think there is a CLI tool already. I remember checking it out when I was building this.