[usrusr]

Most commits are not just text, they are source code. If you had a feasible way to enumerate all the byte sequences that collapse into a given hash value, you might find the subset that is syntactically correct code to be very low. Except if it's Perl, of course.

And the likelihood of all the characters aligning in a way a compiler might find acceptable gets lower with every increase in length of your collisions, so it would be extremely unlikely that the shortest nontrivial match (for both the hash and for code sanity) would not be the right one. The code constraint certainly would not make it easier to find the collision in the first place, but it would give you great confidence in the result of you did.