cli/install: add option to specify alternative kexec url

pkgs/clan-cli/clan_cli/machines/install.py

@@ -1,5 +1,6 @@
 import argparse
 import subprocess
+from dataclasses import dataclass
 from pathlib import Path
 from tempfile import TemporaryDirectory
 
@@ -8,7 +9,7 @@ from ..nix import nix_shell
 from ..secrets.generate import generate_secrets
 
 
-def install_nixos(machine: Machine) -> None:
+def install_nixos(machine: Machine, kexec: str | None = None) -> None:
     h = machine.host
     target_host = f"{h.user or 'root'}@{h.host}"
 
@@ -26,32 +27,55 @@ def install_nixos(machine: Machine) -> None:
         upload_dir.mkdir(parents=True)
         machine.run_upload_secrets(upload_dir)
 
+        cmd = [
+            "nixos-anywhere",
+            "-f",
+            f"{machine.flake_dir}#{flake_attr}",
+            "-t",
+            "--no-reboot",
+            "--extra-files",
+            str(tmpdir),
+        ]
+        if kexec:
+            cmd += ["--kexec", kexec]
+        cmd.append(target_host)
+
         subprocess.run(
             nix_shell(
                 ["nixpkgs#nixos-anywhere"],
-                [
+                cmd,
-                    "nixos-anywhere",
-                    "-f",
-                    f"{machine.flake_dir}#{flake_attr}",
-                    "-t",
-                    "--no-reboot",
-                    "--extra-files",
-                    str(tmpdir),
-                    target_host,
-                ],
             ),
             check=True,
         )
 
 
-def install_command(args: argparse.Namespace) -> None:
+@dataclass
-    machine = Machine(args.machine, flake_dir=args.flake)
+class InstallOptions:
-    machine.deployment_address = args.target_host
+    flake: Path
+    machine: str
+    target_host: str
+    kexec: str | None
 
-    install_nixos(machine)
+
+def install_command(args: argparse.Namespace) -> None:
+    opts = InstallOptions(
+        flake=args.flake,
+        machine=args.machine,
+        target_host=args.target_host,
+        kexec=args.kexec,
+    )
+    machine = Machine(opts.machine, flake_dir=opts.flake)
+    machine.deployment_address = opts.target_host
+
+    install_nixos(machine, kexec=opts.kexec)
 
 
 def register_install_parser(parser: argparse.ArgumentParser) -> None:
+    parser.add_argument(
+        "--kexec",
+        type=str,
+        help="use another kexec tarball to bootstrap NixOS",
+    )
     parser.add_argument(
         "machine",
         type=str,