Re: Improvement: `git-maintenance` to allow configuring of remotes to fetch

[Patrick Steinhardt <ps@pks.im>]

On Mon, Aug 26, 2024 at 05:20:50PM +0530, Shubham Kanodia wrote:
> `git-maintenance` aims to improve the health & performance of
> especially large git repositories.
> A part of git maintenance tasks is `prefetch`.
> 
> However, at the moment, it prefetches all objects from all branches —
> 
> > The prefetch task updates the object directory with the latest objects from all registered remotes.
> 
> This seems non-optimal for repositories where users use the main
> repository to fork branches (instead of personal forks) as the remote
> could have thousands of refs and objects from branches that a user may
> not care about, leading to a very large prefetch dir.
> 
> For large repositories, it might instead be helpful to only fetch
> objects on `main` or `master` because those are the ones most likely
> to be used by users.
> 
> To this effect, git maintenance should perhaps expose a
> maintenance.prefetch.refs setting that subsets prefetching only to
> certain references.

I think that this makes sense as an addition. We would have to think
about things like globbing and whatnot, such that we can say e.g. to
prefetch only tags, only branches or only a subset thereof. We may even
decide to use refspecs here, which could be the most flexible way of
configuring this. We already use the default refspecs anyway -- the only
thing we change is that we prefix the refspec destination with
"refs/prefetch/". So allowing the user to override the refspec used for
prefetching makes sense.

It opens up another question though: if you've got multiple remotes in a
repository, do we also want to make it configurable which of these
should be fetched from? And if you do, do you want to allow configuring
refs to fetch per remote? I guess the answer to both of these questions
would be "yes".

> Is this something that has been raised before / is in works by any
> chance or something that would be an acceptable contribution?

I'm not aware of any discussion around this, and think that this feature
does make sense indeed.

Patrick