On Mon, Feb 07, 2022 at 12:57:55PM -0800, Junio C Hamano wrote:
> You are solving a different problem: "I have this tar archive; what
> git tree object would I get if I extract this archive to an empty
> directory and said 'git add . && git write-tree'?".
>
> I agree that one is computable.
So, I was brainstorming about this today, and I'm curious if you think this
would be a useful feature to have, maybe even natively?
E.g. here's a scenario:
"git archive -S <signed-object>" creates an additional file that is added to
the generated tar/zip archive -- for example, a ${prefix}.GIT_ARCHIVE_SIG. That
file contains the raw contents of the signed tag and/or the signed commit.
"git verify-archive" would look for a toplevel .GIT_ARCHIVE_SIG file. If it's
present, it would verify the signature on these "detached" signed objects to
get a trusted tree hash. Then it would compute the tree hash of the tar
archive (minus the .GIT_ARCHIVE_SIG file) to see if it matches.
In my mind, that would provide the following benefits over the current
practice of detached .sig files:
1. environments like github/git.kernel.org would be able to create verifiable
snapshot archives using an existing set of signed objects
2. packagers would be able to perform cryptographic verification without
needing to track any extra sources like corresponding .sig files; they
would just need to add a build-time dependency on git (plus whatever it
calls for cryptographic verification, such as gnupg or openssh)
3. this would automatically support all git-native signature mechanisms like
openssh and whatever else gets added in the future
Does this idea have any merit, or is it too fragile/crazy to bother?
> Of course, even that reverse problem will break once we consider the
> release tarball generation procedure where we _add_ some generated
> files that are not in the Git tree, for builder's convenience.
Yes, but it's increasingly rare and many build instructions now specifically
allow for things like "first, run autoconf if you don't already have a
configure file", etc.
-K
