Re: Questions about the hash function transition

[Edward Thomson <ethomson@edwardthomson.com>]

On Tue, Aug 28, 2018 at 2:50 PM, Ævar Arnfjörð Bjarmason
<avarab@gmail.com> wrote:
> If we instead had something like clean/smudge filters:
>
>     [extensions]
>         objectFilter = sha256-to-sha1
>         compatObjectFormat = sha1
>     [objectFilter "sha256-to-sha1"]
>         clean  = ...
>         smudge = ...
>
> We could apply arbitrary transformations on objects through filters
> which would accept/return some simple format requesting them to
> translate such-and-such objects, and would either return object
> names/types under which to store them, or "nothing to do".

If I'm understanding you correctly, then on the libgit2 side, I'm very much
opposed to this proposal.  We never execute commands, nor do I want to start
thinking that we can do so arbitrarily.  We run in environments where that's
a non-starter

At present, in libgit2, users can provide their own mechanism for running
clean/smudge filters.  But hash transformation / compatibility is going to
be a crucial compatibility component.  So this is not something that we
could simply opt out of or require users to implement themselves.

-ed