From: Simon Richter <simon.richter@hogyros.de>
Date: Tue, 28 Apr 2026 11:32:37 GMT
Subject: Re: Git generated tarballs and Debian
Message-ID: <a54d57b6-9270-406a-9056-ffaa939c6c21@hogyros.de>
In-Reply-To: <afCLFJX86yEPKKfk@fruit.crustytoothpaste.net>

Hi,

On 4/28/26 7:25 PM, brian m. carlson wrote:

> I'll just note that we don't make any guarantees that `git archive`
> produces identical output across versions.  Incorrectly making that
> assumption broke kernel.org when we changed the format in the past.

Exactly -- that's why I read the tarball and calculate the checksum of 
the corresponding tree object, but we have a few cases where we need 
extra information that isn't in the archive, and I'm wondering where to 
put that extra information: inside the archive itself, or into an extra 
file.

> Also, if you use `export-subst`, then it's possible to emit short object
> IDs, which can differ in length depending on how many objects are in the
> repository.  It's also possible to use zlib or pigz instead of gzip to
> produce tarballs, in which case the compressed data will also differ.

export-subst breaks verification completely as soon as a blob changes.

Compression isn't an issue, because we're comparing tree checksums.

    Simon