Wouldn't that be a red flag if they don't have any public code at all as a senior developer? They aren't fresh out of school or just starting their careers. They should have something.
I just take tabs and rearrange them for personal use. Learn from my mistake and just post whatever to your github, if you fret over its usefulness or purpose you might just never grow your portfolio at all. This was a mistake. You don't have to have some gnu front-page exploratory project.
If you want to shred guitar look up Troy Grady to grok efficient mechanics that won't break your wrist (we type alot for work as well)