Even if SHA-1 were weakened considerably, this would not impact this particular use case all that much... except in cases where git hashes are used in a security-critical way. (Which is probably not that great an idea...)
Doesn't a signed git tag rely on signing the 160-bit hash? So if SHA-1 was really weakened, you could reuse a signature by generating a repo that hashes to the same value as the signed one?
> git hashes are used in a security-critical way
Verifying the integrity of the source code of e.g. the Linux kernel is pretty security-critical.
Unless you are trying to make a joke with the title of the post, sha-1 not related to certificates will be unaffected.
Unaffected by Microsoft's announcement, yes. However, they will be affected by any successful preimage [edit: or collision] attacks on SHA-1, and the possibility of such an attack appears to motivate Microsoft's announcement.