Re: clone (single) commit id?

From: Jeff King <peff@peff.net>
Date: Aug 17, 2023, 19:56 UTC
Message-ID: <20230817195641.GD3032779@coredump.intra.peff.net>
In-Reply-To: <CABtpZSGcL8hkk3HA3ECtt7KeLPOhuB0n7EKN1Tg5ZHpFBE0V0A@mail.gmail.com>

On Thu, Aug 17, 2023 at 09:45:19PM +0200, Patrik Hägglund wrote:

Show 13 quoted lines

> In our CI setup, for reproducibility and performance reasons, I want
> to be able to clone a repository with only a single given commit id
> (commit hash). (Using 'git init' + 'git fetch' + 'git checkout' is
> possible, but more elaborate/low-level.)
> 
> At https://lore.kernel.org/git/MN2PR12MB3616C1F2E97A18547740651DF9E29@MN2PR12MB3616.namprd12.prod.outlook.com/
> it is stated that:
> 
> > Never mind, I see, feature exists but server needs to allow it. Sigh.
> 
> However, I'm not able to find this in the Git documentation. Can
> someone point out how to configure this? Can this be better
> documented?

I'd use a shallow clone with depth 1, like:

  git clone -b $your_branch --depth 1 $remote_url

Note that "--depth" implies --single-branch, so it will really just grab that one branch (and if it's the remote's default branch that you want, you can omit the "-b $your_branch" part).

If you find the shape of history useful (e.g., your CI wants to look at just new commits), you might also find partial clones useful. Something like:

  git clone --filter=blob:none $remote_url

will fetch all commits and trees, but only load blobs on-demand (so basically whatever is needed to check out that tip commit). You can pare it down further by switching to "--filter=tree:0", which will avoid trees (but note that filling in trees when you need them is a bit more expensive, since inherently you have to make a round-trip to the server for each level of tree).

-Peff