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

[Patrick Steinhardt <ps@pks.im>]

On Mon, Sep 02, 2024 at 09:16:24PM +0530, Shubham Kanodia wrote:
> > Patrick Steinhardt <ps@pks.im> writes:
> >
> > > I'm not aware of any discussion around this...
> >
> > I do not think so, either.
> >
> > I agree that it makes as much sense to limit prefetches to a subset
> > of remotes as it makes sense to limit to certain hierarchies (e.g.
> > excluding refs/changes/ or even limiting to refs/heads/seen and
> > nothing else).
> 
> I'm seeking advice on the configuration option structure for this
> feature. The typical config format for maintenance tasks seems to be
> as follows:
> 
> `maintenance.<task-name>.<option>`
> 
> A natural extension of this for the prefetch task could be:
> 
> ```
> git config maintenance.prefetch.<remote-name>.refs refs/heads/master
> ```
> 
> In this structure, the 'refs' value represents only the source part of
> a refspec, and both remote and refs can be configured.
> Specifying a full refspec isn't necessary since the --prefetch option
> may override the destination anyway.
> 
> While I've successfully implemented this approach, I'm open to
> suggestions for alternative configuration options. My concerns are:
> 
> 1. Most Git configurations are nested up to three levels deep, whereas
> this proposal introduces a fourth level.
> 2. This configuration appears in the config file as:
> 
> ```
> [maintenance "prefetch.origin"]
>        refs = refs/heads/master
> ```
> which might look odd?

Agreed, it does. To me, the most natural way to configure this would be
as part of the remotes themselves:

```
[remote "origin"]
    url = https://example.com/repo.git
    fetch = +refs/heads/*:refs/remotes/origin/*
    # Whether or not the prefetch task shall fatch this repository.
    # Defaults to `true`.
    prefetch = true
    # An arbitrary number of refspecs used by the prefetch task.
    # Overrides the fetch refspec if given, otherwise we fall back to
    # using the fetch refspec.
    prefetchRefspec = +refs/heads/main:refs/remotes/origin/main
```

The prefetch refspec would be rewritten by git-maintenance(1) such that
the destination part (the right-hand side of the refspec) is prefixed
with `refs/prefetch/`, same as the fetch refspec would be changed in
this way.

An alternative would be to _not_ rewrite the prefetch refspec at all and
thus allow the user to prefetch into arbitrary hierarchies. But I'm a
bit worried that this might cause users to misconfigure prefetches by
accident, causing it to overwrite their usual set of refs.

> Also, hopefully my mail is formatted better this time!

It is, thanks!

Patrick