Re: [PATCH 0/2] recover from "failed to apply delta"

[Jeff King <peff@peff.net>]

On Fri, Jun 14, 2013 at 02:51:35PM -0700, Junio C Hamano wrote:

> > Here is a re-roll; the first patch is a small cleanup in t5303 that is
> > required for the new tests to work.
> 
> Heh, I was doing the same, but I cheated ;-)
> 
> diff --git a/t/t5303-pack-corruption-resilience.sh b/t/t5303-pack-corruption-resilience.sh
> index 5b1250f..57436db 100755
> --- a/t/t5303-pack-corruption-resilience.sh
> +++ b/t/t5303-pack-corruption-resilience.sh
> @@ -51,7 +51,7 @@ do_corrupt_object() {
>      ofs=`git show-index < ${pack}.idx | grep $1 | cut -f1 -d" "` &&
>      ofs=$(($ofs + $2)) &&
>      chmod +w ${pack}.pack &&
> -    dd of=${pack}.pack count=1 bs=1 conv=notrunc seek=$ofs &&
> +    dd of=${pack}.pack count=${3-1} bs=1 conv=notrunc seek=$ofs &&
>      test_must_fail git verify-pack ${pack}.pack

Yeah, I almost did that, but then I realized that dd will simply read
all of its input, anyway.

>  test_expect_success \
> +    'corrupt delta-part of a packed object, fall back to loose' \
> +    'create_new_pack &&
> +     path=$(echo "$blob_3" | sed -e "s|^\(..\)|\1/|") &&
> +     cat ".git/objects/$path" >saved &&
> +     git prune-packed &&
> +
> +     dd if=${pack}.idx bs=1 count=20 skip=1032 >blob1-bin &&
> +     dd if=${pack}.pack bs=1 count=20 skip=2233 >blob3-delta-base-bin &&
> +
> +     # At the beginning of the REF_DELTA representation of $blob_3,
> +     # write 20-byte base object name for $blob_1, instead of $blob_2.
> +     # The binary representation of object name for $blob_1 is found
> +     # at offset 4 + 4 + 256*4 = 1032 for 20 bytes.
> +     dd if=${pack}.idx bs=1 count=20 skip=1032 | do_corrupt_object $blob_3 2 20 &&
> +     test_must_fail git cat-file blob $blob_3 >/dev/null &&

I didn't want to bother coming up with the binary version of the
REF_DELTA sha1, so I used OFS_DELTA. :)

-Peff