Re: FW: Git pulls failing on ia64 test tree?

From: Junio C Hamano <junkio@cox.net>
Date: Sep 14, 2005, 17:25 UTC
Message-ID: <7vk6hjlfxw.fsf@assigned-by-dhcp.cox.net>
In-Reply-To: <7vbr2vob6w.fsf@assigned-by-dhcp.cox.net>

Junio C Hamano <junkio@cox.net> writes:

Show 10 quoted lines

> "Luck, Tony" <tony.luck@intel.com> writes:
>
>> I've set up objects/info/alternates to point at linus' tree and deleted
>> all the packs from my tree.  The web view at kernel.org/git looks ok,
>> so I think those changes are ok.
>>
>> So what am I missing?
>
> Let me take a look at your tree on master while I'll try to pull
> from your public tree and see if I can reproduce.

Ah, you deleted packs from your repository, which I missed when I first saw your message.

The objects/info/alternates mechanism is currently only known to the git that operates on the machine that has the file -- client side does not make use of that information. That means only git-daemon and 'git native protocol over ssh' (not the commit walker ssh-fetch) can deal with such a repository right now, because they run git on the side your repository is. Gitweb also obviously runs git on the machine a copy of repository is, so you would not see problems.

The recommendation by Linus to "point him with alternate to borrow his objects" is a sound one in the long term, but I think it was a bit premature in practice -- the client side tools are not ready for that yet. From the original error report:

 > error: Could not read 9401c705f2a6a7e5df102f6443dba395c3c5e5a8
 > error: Could not read 357d596bd552ad157a906289ab13ea6ba7e66e3d
 > Updating from aa2dca4563b0629ecd9d9994dfdf39f29ff1b43f to 
6c141f61ee4f5fba63d9c54e03cb2faa6877bf1a.
 > fatal: failed to unpack tree object 6c141f61ee4f5fba63d9c54e03cb2faa6877bf1a
 > $

The first two "Could not read" are talking about objects only found in Linus' repository -- your objects/ hierarchy does not have them. Rsync transport slurps everything under _your_ objects/ hierarchy [*1*] and does not know that your objects/ hierarchy is incomplete and needs to borrow from Linus' objects/ directory. If the downloader has the objects found in Linus' repository that is fine but otherwise he has problems.

As a workaround, please do this:

    cd /pub/scm/linux/kernel/git/aegl/linux-2.6.git/
    ln ../../torvalds/linux-2.6.git/objects/pack/* objects/pack/.
    mv objects/info/alternates objects/info/alternates+
    GIT_DIR=. git fetch ../../torvalds/linux-2.6.git/
    GIT_DIR=. git fsck-objects
    mv objects/info/alternates+ objects/info/alternates

The 'git fetch' step would complain about a couple of commits you have but there is no need to worry -- we are deliberately "corrupting" your repository by temporarily moving alternates away so that it can fetch missing objects from Linus repository. The fsck-objects should then report no missing objects.

Sorry for this very unpleasant experience git has caused you X-<.

[Footnotes]

*1* BTW, I just spotted a bug there -- since we now have objects/info subdirectory, we should exclude that when copying.

*2* Ideally I would have liked to do git-relink after 'git fetch' from Linus repo in the above, but it does not seem to want to relink a naked repository... I should bug Ryan about it.