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

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

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 <redacted>
---

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.