[chores] CI bots: cache dependencies

[nemesifier]

The bots always reinstall all the dependencies they need at each run, a huge waste of resources (hardware, network bandwidth, energy, time). We need to cache the dependencies, for the pip deps we can use setup.py for the hash so if anything changes there the cache is invalidated.

[czarflix]

Happy to help with this if useful. If nobody is already on it, I can take a look.

[czarflix]

Happy to help with this if useful. If nobody is already on it, I can take a look.

I think there’s a workable way to do it. Most of the bot workflows seem straightforward to cache with setup.py as the invalidation key, but the changelog bot likely needs a slightly different shape since it goes through a composite action.

[SAMurai-16]

Could you clarify what you mean by a “different shape” for the changelog bot? Are you suggesting a different caching approach than setup-python pip cache keyed by setup.py?

[czarflix]

Could you clarify what you mean by a “different shape” for the changelog bot? Are you suggesting a different caching approach than setup-python pip cache keyed by setup.py?

the changelog bot seems to need a slightly different shape because it goes through a composite action. I tested one approach locally. If maintainers think that direction makes sense, I can open a PR.