Re: [PATCH 02/10] builtin/fast-import: fix segfault with unsafe SHA1

> > > > I think we should perhaps combine forces here. My ideal end-state is to
> > > > have the unsafe_hash_algo() stuff land from my earlier series, then have
> > > > these two fixes (adjusted to the new world order as above), and finally
> > > > the Meson fixes after that.
> > > >
> > > > Does that seem like a plan to you? If so, I can put everything together
> > > > and send it out (if you're OK with me forging your s-o-b).
> > >
> > > I think the ideal state would be if the hashing function used was stored
> > > as part of `struct git_hash_ctx`. So the flow basically becomes for
> > > example:
> > >
> > >     ```
> > >     struct git_hash_ctx ctx;
> > >     struct object_id oid;
> > >
> > >     git_hash_sha1_init(&ctx);
> > >     git_hash_update(&ctx, data);
> > >     git_hash_final_oid(&oid, &ctx);
> > >     ```
> > >
> > > Note how the intermediate calls don't need to know which hash function
> > > you used to initialize the `struct git_hash_ctx` -- the structure itself
> > > should remember what it has been initilized with and do the right thing.
> >
> > I'm not sure I'm following you here. In the stream_blob() function
> > within fast-import, the problem isn't that we're switching hash
> > functions mid-stream, but that we're initializing the hashfile_context
> > structure with the wrong hash function to begin with.
>
> True, but it would have been a non-issue if the hash context itself knew
> which hash function to use for updates. Sure, we would've used the slow
> variant of SHA1 instead of the fast-but-unsafe one. But that feels like
> the lesser evil compared to crashing.