It seems this was considered: https://git-scm.com/docs/hash-function-transition/#_using_hash_functions_in_parallel https://git-scm.com/docs/hash-function-transi

It seems this was considered: https://git-scm.com/docs/hash-function-transition/#_using_hash_functions_in_parallel https://git-scm.com/docs/hash-function-transition/#_using_ha... The biggest one of those downsides I think is that the SHA-1 history could be changed out from under you if a new attack was published.