feature: configurable/extensible tasks

[cmacrae]

Hey again @pinpox 👋 Hope you've been well :)

These changes introduce the lollypops.tasks & lollypops.extraTasks options to the module. See the associated change to the README to get an idea of its use case.

Here's an example of how I'm using it in one such case: macOS with Nix set up, config for all systems kept in my flake. One of my systems is a Raspberry Pi 4B, not all that powerful for building its own system closure. So, using lollypops in my flake, for the host definition of that system I:

• ensure an aarch64 build VM is running on the MacBook (near native perf with Tart)
• (this VM is set up in Nix as a remote builder for aarch64-linux systems)
• instead of running a nixos-rebuild on the Pi remotely, I defer to ruinning nix build locally, which offloads the build tasks to the VM, since it's for an aarch64-linux system
• copy the built closure to the Pi, then instruct it to switch the system profile to this

Details

```nix { nixosConfigurations.net1 = nixpkgs.lib.nixosSystem { system = "aarch64-linux"; modules = commonLinuxConfig ++ [ ./bases/net1.nix ./bases/server.nix { lollypops.deployment.local-evaluation = true; lollypops.secrets = { files = { "net1/wireguard-privatekey" = { }; "net1/acme-dnsimple-envfile" = { }; }; }; # Use `nix-build` to rely on build1 VM lollypops.tasks = [ "deploy-secrets" "rebuild" ]; lollypops.extraTasks = { bootstrap-builder = { deps = [ "check-vars" ]; desc = "Ensure the build VM is running"; cmds = [ '' { tart list --format json | jq -e '.[]|select(.Name=="build1")|any' > /dev/null; } || \ { echo "No VM called 'build1' found..." ; exit 1; } '' '' if tart list --format json \ | jq -e '.[]|select(.Name=="build1" and .Running==true)|any' \ > /dev/null; then echo "build1 is up..."; else echo "booting build1..." nohup tart run --no-graphics --net-bridged=en0 --rosetta="rosetta" build1 >/dev/null 2>&1 & count=0 max_tries=15 echo "Waiting for build1 to come up..." while [ $count -lt $max_tries ]; do if nc -vz build1 22 > /dev/null 2>&1; then echo "Looks like build1 is ready!" exit 0 fi count=$((count + 1)) sleep 1 done echo "Failed after $max_tries attempts." exit 1 fi '' ]; }; rebuild = { dir = "."; deps = [ "bootstrap-builder" ]; desc = "Rebuild configuration of: net1"; cmds = [ '' nix build -L \ ${self}#nixosConfigurations.net1.config.system.build.toplevel && \ REAL_PATH=$(realpath ./result) && \ nix copy -s --to ssh://admin@net1 $REAL_PATH 2>&1 && \ ssh admin@net1 \ "sudo nix-env -p /nix/var/nix/profiles/system --set $REAL_PATH && \ sudo /nix/var/nix/profiles/system/bin/switch-to-configuration switch" '' ]; }; }; } ]; }; } ```

These added features have proven really useful for doing something like this, rather than having to figure out awkward ways of implementing it as nuanced feature with a bunch of conditionals.

I'm not tied to any implementation details, namings or descriptions. So please do feel free to suggest any changes you'd like to see :) I've done thorough testing and it all seems to work nicely

[pinpox]

Hey @cmacrae!

Thanks for the contribution and sorry it took me so long to answer, I was away for some time. This looks really awesome, I have been thinking about something like this myself (see the now deleted TODO comment).