Both IPFS and blockchain are definitely applicable to decentralizing applications. E.g. DSound[0], a distributed version of Soundcloud is built with IPFS + a blockchain(not necessarily a fan of STEEM though). There could just as well be something analogous for Github, Bitbucket, etc..
[0]: https://steemit.com/music/@prc/introducing-dsound-a-decentra...
You can also leave stuff like that out, but then you will end up with a system where everyone can only push to their own forks leaving us with a very splintered distributed system. To compensate we would need a much better system for distributed content discovery than anything I've seen so far.
Giving readable names to repositories is a possible use case, although I'd just use DNS.