Re: pack corruption post-mortem

On Wed, Oct 16, 2013 at 3:34 PM, Jeff King [off-list ref] wrote:

I was recently presented with a repository with a corrupted packfile,
and was asked if the data was recoverable. This post-mortem describes
the steps I took to investigate and fix the problem. I thought others
might find the process interesting, and it might help somebody in the
same situation.

I started with an fsck, which found a problem with exactly one object
(I've used $pack and $obj below to keep the output readable, and also
because I'll refer to them later):

    $ git fsck
    error: $pack SHA1 checksum mismatch
    error: index CRC mismatch for object $obj from $pack at offset 51653873
    error: inflate: data stream error (incorrect data check)
    error: cannot unpack $obj from $pack at offset 51653873

I wonder if we should protect the sha-1 and pathname tables in packv4
with CRC too. A bit flipped in there could cause stream of corrupt
objects and make it hard to pinpoint the corrupt location..
-- 
Duy