Pin package versions? Use snapshot archives?

I'm new to `chisel`, so my understanding may be wrong. But it seems like packages are always picked from the "latest" available version. While this may be good for experimenting, it doesn't help making stable (read: reproducible) builds.

Is it possible to pin package versions? Is it possible to use snapshot archives?

From a quick look at the source code, it seems like [repositories are hardcoded](https://github.com/canonical/chisel/blob/main/internal/archive/archive.go#L129). If so, are there any plans to offer alternatives in these areas?