Context & working on improving caching in my CIs

[mbarbin]

I have been experimenting with nightly for a bit lately and wanted to give you some context as to where I am coming from, and where I hope to head next.

A few months ago, I started publishing some packages to opam and have been trying to set up more CI jobs for my repos on GitHub.

Here is a screenshot of my GHA minutes bill.

The way GitHub presents this dated, for example:

Gross:    $63.21
Billed:   $0
Discount: $63.21

I'm not positive on where the discount comes from, but regardless, I'd be happy to switch to an improved setup for the future.

When a bill/time curve shows that kind of trend, it usually calls for some actions. Although in this instance, I think it's all good (see below).

The majority of my GHA time is consumed by fetching and building compilers and dependencies.

Last time I researched open issues about opam and caches for GHA, I concluded that this was a hard problem.

I'm now hoping that the built-in caching in dune-pkg would come to the rescue. My impression is that my usage will drop back to almost zero.

I've started experimenting with this, so you might see me opening some issues here and there as I pursue that goal. This will be a side project for a gradual transition over time. Thanks!