Comment by williamstein

A really critical sneaky trick that Linus pulled in the implementation of Git was to just pretend like Sha1 hashes never collide, which helped make "cheap branching, robust conflict management, and offline workflows" possible. This (false but convenient) assumption massively reduced the complexity of many algorithms, and allowed Git to efficiently do things that other source control systems couldn't do. I personally switched from Darcs to Git about 15 years ago entirely due to performance issues.