Re: [PATCH/RFC] Allow writing loose objects that are corrupted in a pack file

From: R. Tyler Ballance <tyler@slide.com>
Date: Dec 9, 2008, 09:02 UTC
Message-ID: <1228813339.18611.35.camel@starfruit.local>
In-Reply-To: <20081209093627.77039a1f@perceptron>

On Tue, 2008-12-09 at 09:36 +0100, Jan Krüger wrote:

Show 14 quoted lines

> For fixing a corrupted repository by using backup copies of individual
> files, allow write_sha1_file() to write loose files even if the object
> already exists in a pack file, but only if the existing entry is marked
> as corrupted.
> 
> Signed-off-by: Jan Krüger <jk@jk.gs>
> ---
> 
> On IRC I talked to rtyler who had a corrupted pack file and plenty of
> object backups by way of cloned repositories. We decided to try
> extracting the corrupted objects from the other object database and
> injecting them into the broken repo as loose objects, but this failed
> because sha1_write_file() refuses to write loose objects that are
> already present in a pack file.

Figured I'd chime in here with some anecdotal evidence with the error condition that I hit shortly after Jan sent the email.

        xdev3 (master-release)% git pull --no-ff . master
        From .
         * branch            master     -> FETCH_HEAD
        error: failed to read object
        befd9bc4d184b4383569909e4d245f3337c1f8ed at offset 1415784644
        from .git/objects/pack/pack-f7eb06e39f01b528c1d1a2c413ac51b31b8515aa.pack
        fatal: object befd9bc4d184b4383569909e4d245f3337c1f8ed is
        corrupted
        Merge with strategy recursive failed.
        xdev3 (master-release)%

I ran that command a couple of times to make sure it wasn't a fluke, I
repeated the error numerous times (without switching branches or pulling
from a remote). This pull was done with a slightly modified internal
version of v1.6.0.4
        xdev3 (master-release)% git --version
        git version 1.6.0.4-kb1
        xdev3 (master-release)

After consulting with Jan, I tried running the same command with a
modified version of v1.6.0.5 with Jan's patch
        xdev3 (master-release)% ~/basket/bin/git pull --no-ff . master
        From .
         * branch            master     -> FETCH_HEAD
        Merge made by recursive.
         ** TOP SECRET MERGES! ;) **
        
         13 files changed, 51 insertions(+), 21 deletions(-)
        xdev3 (master-release)%
        
        
Purely anecdotal as I'm not entirely clear what the hell is actually going on here :)

Cheers

-- 
-R. Tyler Ballance
Slide, Inc.