there are two problems we need to solve:

1. github is not the repo only. It is an ecosystem for developing projects with bug tracking, issues, voting, comments, reviews, etc.
To create a decentralized clone of github you'll need to reproduce all that features.

2. to create a distributed decentralized repo hosting you need to create a storage with multiple times duplicated data. GitHub is free for opensource projects and paid features for private projects. How that can be reproduced in distributed ecosystem?