1) We are talking about sha1, md5 is out of topic

2) This is the main topic ! Being able to generate >>valid code<< with a >>specific purpose<< , so that GIT have to change its hashing algorithm;

3) A.K.A your answer is total nonsense.

Everyone else, ok, I'm listening, give proof that you can change code on GitHub stealthy messing with hashing, moreover inserting a "payload" creating a SHA-1 collision in a reasonable computational time, everything else is BS.