Re: USE_SHA1DC is broken in pu

>   Side note: I also have a feeling that any operation that cares about
>   non-object sha1 performance is probably ripe for other, bigger
>   optimizations. If you update 300MB worth of index entries, then the
>   cost of computing a checksum over it isn't a big deal. But if you have
>   a 300MB index file and you update one entry (or you just want to read
>   one entry), maybe we ought to consider solutions that don't involve
>   the whole 300MB in the first place. I know that's a much harder change
>   because it may involve new on-disk formats. But it seems like that's
>   the right long-term path forward.