Collision isn't a spooky action at distance. Even if they tricked the victim into accepting a file they have a collision for, they still can't do anything nefarious. Attack requires an opportunity to replace the colliding file with its evil twin, and that requires write access to victim's repository or tricking the victim into re-fetching their files from an attacker-controlled repository.

Besides, the known collision attack generates files with blocks of binary garbage, which makes it difficult to trick someone into accepting. It won't look like source code, and if someone accepts binary blobs of executable code, you don't need collisions to pwn them.