Re: Mirror repositories for submodules

From: Simon Richter <simon.richter@hogyros.de>
Date: Jun 4, 2026, 05:11 UTC
Message-ID: <d64e7f31-4e00-478c-ab31-b671242865fb@hogyros.de>
In-Reply-To: <xmqqcxy7qfgk.fsf@gitster.g>

Hi,

On 6/4/26 10:09 AM, Junio C Hamano wrote:

Show 5 quoted lines

> So, no, I do not think a contribution to add mirror repositories as
> alternate submodule sources should be considered for inclusion, as
> it artificially limits usefulness of the feature.  A feature to add
> mirror repositories as alternate sources might be worth considering,
> though.

This is relevant to the Debian use case: we run a git server that archives git trees for Debian packages, and ideally the objects on this server should be identical to what you get from upstream projects.

This is a big problem for archiving projects that use submodules, because we cannot alter the reference URLs.

Cloning from our server will, depending on what upstream uses, either a relative URL (which will go to our server, but we have little control over what the name part of the repository base URL is going to be), or an absolute URL that instructs clients to pull from another place, which conflicts with our goal to have a self-contained archive.

The idea posited earlier, to have a "repository identity" that remains the same across forks and clones, is somewhat appealing, but the best idea I can come up with is generating some kind of repository UUID, and adding a symlink -- not a great design because it pollutes outside the repo:

     $ mkdir myproject
     $ cd myproject
     $ git init
     $ ls -l ..
     lrwxrwxrwx 1 simon simon   9 Jun  4 14:05 
12345678-9abc-def0-1234-56789abcdef0.git -> myproject
     drwxrwxr-x 2 simon simon  40 Jun  4 14:04 myproject

On the other hand, this can be used to construct a stable relative submodule URL.

Making the symlinks optional would require keeping a list of local clones and their UUIDs, and resolving them.

I don't like that design, but as I said it's the best idea I have for now.

I also fully expect that Debian's servers will be used by a lot of people outside the project as soon as it becomes a convenient fallback, in the same way people are pulling .orig.tar.gz archives from Debian mirrors, so we need to make it easy to set up a mirror, to allow this to scale.

    Simon