[BjoernKW]

Git already provides a proof-of-PR with its commit history. You can have a look at someone's GitHub profile so see the projects that person has contributed to.

While it's not a permanent record you'd have to go to great lengths to permanently delete someone's effort from the record. You could also still keep the repositories for yourself on some local machine as a permanent record.

The permanent, tamper-proof record feature of blockchains only provides a significant benefit if many or all players in the game have an incentive to tamper with the data in the first place.