>"incredible amount of compute power to generate a collision"
That article sets the "best case", not the worse, and that article is "old". The GPU/ASIC industry is bananas, and we have no idea what other breaks there are. MD5 is a great example of how quickly these things become dangerous.
SHA1 was a terrible choice when git was made, it's a horrific one now. SHA1 cannot be used for anything security sensitive. That domain is always larger than what we may first suspect.
>the alternative is... do nothing?
No, the alternative is to use gpg with a secure hash over and above anything git provides. This is a bad choice because there is no standardized git infrastructure built around anything secure.
This fragments the industry (like Go building their own, again) where git could instead continue to unify, making an interface that has a lot of eyeballs, visibility, and a secure, universal implementation. Instead, fragmentation remains the solution. Git could have easily taken care of this by simply listening to people back in ~2005 saying, "gee, maybe we shouldn't use a hash that's already on its deathbed". https://www.schneier.com/blog/archives/2005/02/cryptanalysis...
It would be nice just have used SHA-256. I hope Snowden didn't show us nothing.