Code is a well-chosen piece of logic to make sense as a whole. You can't just arbitrarily take to pieces of code and mash them together just because two random developers on the planet happened to write them one after the other in a sequential fashion of time.

E.g if you ask a classroom "What's 1 + 1 ?" then someone might say "3" right after you asked but before someone else says "2", but that does not make "3" right.

Proper order of commits is established by a MUCH more simple mechanism in fact: A git commit includes the hash of the previous commit in the history.

So the plain aspect of "storing some bytes" is needed, not a blockchain :) As someone else said, Git provides just that.

FWIW, censorship-resistant networks such as the aforementioned Freenet can and are used to publish Git repositories in a robust fashion. But no blockchain magic is required here either :)