Chances of a sha1 collision are so low that all the git repos in the world combined are still astronomically unlikely to collide at all. You'd need 2^80 git objects to exist for a collision to be likely, which would require roughly 100 quadrillion git repos the size of the linux kernel repo. Storing just the shas of those objects would require 50 yottabytes of disk space, let alone storing the object values.



This kind of system should still not be designed to use shaN. Use multihash so you can upgrade ifwhen collision generation becomes feasible. (As ipfs does.)