feat(ci): base for VMs for better testing

.forgejo/ci-files/border.nix

@@ -0,0 +1,4 @@
+{ lib, pkgs, ... }:
+{
+  networking.hostName = "border-vm";
+}

.forgejo/ci-files/client.nix

@@ -0,0 +1,4 @@
+{ lib, pkgs, ... }:
+{
+  networking.hostName = "client-vm";
+}

.forgejo/ci-files/default.nix

@@ -0,0 +1,40 @@
+{
+  pkgs ? (import <nixpkgs> { }),
+  lib ? pkgs.lib,
+}:
+let
+  base-cmd = vm: ''
+    ${pkgs.qemu}/bin/qemu-system-x86_64 -m 4G \
+            -kernel ${vm.kernel}/bzImage \
+            -initrd ${vm.ramdisk}/initrd \
+            -append "init=${vm.toplevel}/init loglevel=4 console=ttyS0" \
+            -display none -serial mon:stdio
+  '';
+
+  border-vm =
+    (import (pkgs.path + "/nixos/lib/eval-config.nix") {
+      system = "x86_64-linux";
+      modules = [
+        ./border.nix
+        ./vm-base.nix
+      ];
+    }).config.system.build;
+
+  client-vm =
+    (import (pkgs.path + "/nixos/lib/eval-config.nix") {
+      system = "x86_64-linux";
+      modules = [
+        ./client.nix
+        ./vm-base.nix
+      ];
+    }).config.system.build;
+
+  border-launch = pkgs.writeShellScript "lauch-border" ''
+    ${base-cmd border-vm}
+  '';
+
+  client-launch = pkgs.writeShellScript "lauch-client" ''
+    ${base-cmd client-vm}
+  '';
+in
+{ }

.forgejo/ci-files/vm-base.nix

@@ -0,0 +1,92 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+let
+  sqshStore = pkgs.callPackage (pkgs.path + /nixos/lib/make-squashfs.nix) {
+    storeContents = [
+      config.system.build.toplevel
+    ];
+    comp = null; # no time for this
+  };
+in
+{
+  system.build.ramdisk = pkgs.makeInitrdNG {
+    inherit (config.boot.initrd) compressor;
+    prepend = [ "${config.system.build.initialRamdisk}/initrd" ];
+
+    contents = [
+      {
+        source = sqshStore;
+        target = "/nix-store.squashfs";
+      }
+    ];
+  };
+
+  fileSystems = {
+    "/" = {
+      fsType = "tmpfs";
+      options = [ "mode=0755" ];
+    };
+
+    "/nix/.ro-store" = {
+      fsType = "squashfs";
+      device = "../nix-store.squashfs";
+      options = [ "loop" ];
+      neededForBoot = true;
+    };
+
+    "/nix/.rw-store" = {
+      fsType = "tmpfs";
+      options = [ "mode=0755" ];
+      neededForBoot = true;
+    };
+
+    "/nix/store" = {
+      overlay = {
+        lowerdir = [ "/nix/.ro-store" ];
+        upperdir = "/nix/.rw-store/store";
+        workdir = "/nix/.rw-store/work";
+      };
+      neededForBoot = true;
+    };
+  };
+
+  boot = {
+    loader.grub.enable = false;
+    initrd = {
+      availableKernelModules = [
+        "squashfs"
+        "overlay"
+      ];
+
+      kernelModules = [
+        "loop"
+        "overlay"
+      ];
+    };
+    postBootCommands = ''
+      # After booting, register the contents of the Nix store
+      # in the Nix database in the tmpfs.
+      ${config.nix.package}/bin/nix-store --load-db < /nix/store/nix-path-registration
+    '';
+  };
+
+  services = {
+    getty.autologinUser = lib.mkForce "root";
+    openssh.enable = true;
+    qemuGuest.enable = true;
+  };
+  nix = {
+    nixPath = [
+      "nixpkgs=${builtins.storePath pkgs.path}"
+      "nixos=${builtins.storePath pkgs.path}"
+    ];
+    channel.enable = false;
+    settings.nix-path = config.nix.nixPath;
+    package = pkgs.lix;
+  };
+  console.keyMap = "fr";
+}