Use krops for deployments

lib/krops.nix

@@ -0,0 +1,31 @@
+{ hostname
+, target ? null
+, extraSources ? { }
+}:
+let
+  sources = import ../nix/sources.nix;
+  krops = sources.krops;
+  lib = import "${krops}/lib";
+  pkgs = import "${krops}/pkgs" { };
+
+  source = lib.evalSource [
+    ({
+      nixpkgs.git = {
+        ref = sources.nixpkgs.rev;
+        url = https://github.com/NixOS/nixpkgs;
+        shallow = true;
+      };
+      config.file = toString ../.;
+      nixos-config.symlink = "config/machines/${hostname}/configuration.nix";
+    } // extraSources)
+  ];
+in
+pkgs.krops.writeDeploy "deploy-${hostname}" {
+  source = source;
+  target = lib.mkTarget (if target == null then "root@${hostname}" else target) // {
+    extraOptions = [
+      # force allocation of tty to allow aborting with ^C and to show build progress
+      "-t"
+    ];
+  };
+}

machines/nunotaba/krops.nix

@@ -0,0 +1,3 @@
+import ../../lib/krops.nix {
+  hostname = "nunotaba";
+}

machines/sayuri/krops.nix

@@ -0,0 +1,3 @@
+import ../../lib/krops.nix {
+  hostname = "sayuri";
+}

nix/sources.json

@@ -1,4 +1,16 @@
 {
+    "krops": {
+        "branch": "master",
+        "description": "Mirror of https://cgit.krebsco.de/krops/about/ (PRs / issues accepted, as can be seen by not having them disabled)",
+        "homepage": "",
+        "owner": "krebs",
+        "repo": "krops",
+        "rev": "c207e1f71b85d7ed20f6bc8d91704ceec09ea5ef",
+        "sha256": "11rk7i7vy788sxhhngj9951z36y5y6l83szidjglw7czhff9rrbc",
+        "type": "tarball",
+        "url": "https://github.com/krebs/krops/archive/c207e1f71b85d7ed20f6bc8d91704ceec09ea5ef.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
     "nixpkgs": {
         "branch": "nixos-20.09",
         "description": "Nix Packages collection",