Re: Verifiable git archives?

From: Junio C Hamano <gitster@pobox.com>
Date: Jan 9, 2014, 20:11 UTC
Message-ID: <xmqqsiswapav.fsf@gitster.dls.corp.google.com>
In-Reply-To: <CALCETrU88evB6VQrE8=8vrc+HYXAX8_Zx7TsYZp6YXeE4dZdvg@mail.gmail.com>

Andy Lutomirski <luto@amacapital.net> writes:

Show 11 quoted lines

> It's possible, in principle, to shove enough metadata into the output
> of 'git archive' to allow anyone to verify (without cloning the repo)
> to verify that the archive is a correct copy of a given commit.  Would
> this be considered a useful feature?
>
> Presumably there would be a 'git untar' command that would report
> failure if it fails to verify the archive contents.
>
> This could be as simple as including copies of the commit object and
> all relevant tree objects and checking all of the hashes when
> untarring.

You only need the object name of the top-level tree. After "untar" the archive into an empty directory, make it a new repository and "git add . && git write-tree"---the result should match the top-level tree the archive was supposed to contain.

Of course, you can write "git verify-archive" that does the same computation all in-core, without actually extracting the archive into an empty directory.