hydra: actually use version from flake

flake.lock

@@ -144,11 +144,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1718119663,
-        "narHash": "sha256-36+umLoMsx0ZHNcuTNAhmRTw3JoyaIS9vOy9NnKRPhQ=",
+        "lastModified": 1719253535,
+        "narHash": "sha256-HE0QHbOEfmmiFRBtWy+7pTlaDolxDfo5mgPcV20KOGA=",
         "ref": "refs/heads/main",
-        "rev": "cbe527a3ee6256de0c5bde5b10821f5095b60e22",
-        "revCount": 4170,
+        "rev": "e9d0a3a754d5a477126ecb3c0bac3bf91a5bb189",
+        "revCount": 4171,
         "type": "git",
         "url": "https://git.lix.systems/lix-project/hydra.git"
       },
@@ -169,11 +169,11 @@
         "pre-commit-hooks": "pre-commit-hooks"
       },
       "locked": {
-        "lastModified": 1718081112,
-        "narHash": "sha256-3cpIVHuyo6yz9n7U/7U/p2Lmwjj1xHdTJR2RkT5JntY=",
+        "lastModified": 1719211568,
+        "narHash": "sha256-oIgmvhe3CV/36LC0KXgqWnKXma39wabks8U9JBMDfO4=",
         "ref": "refs/heads/main",
-        "rev": "8a3d063a494c4b8c767190a5ce3e4075a75f9d07",
-        "revCount": 15756,
+        "rev": "4c3d93611f2848c56ebc69c85f2b1e18001ed3c7",
+        "revCount": 15877,
         "type": "git",
         "url": "https://git@git.lix.systems/lix-project/lix"
       },
@@ -251,6 +251,10 @@
         "agenix": "agenix",
         "colmena": "colmena",
         "hydra": "hydra",
+        "lix": [
+          "hydra",
+          "nix"
+        ],
         "nixpkgs": "nixpkgs"
       }
     },

flake.nix

@@ -12,12 +12,18 @@
 
     hydra.url = "git+https://git.lix.systems/lix-project/hydra.git";
     hydra.inputs.nixpkgs.follows = "nixpkgs";
+
+    lix.follows = "hydra/nix";
   };
 
   outputs = { nixpkgs, ... } @ inputs: {
     colmena = {
       meta.nixpkgs = import nixpkgs {
         system = "x86_64-linux";
+        overlays = [
+          inputs.hydra.overlays.default
+          inputs.lix.overlays.default
+        ];
       };
       meta.specialArgs.inputs = inputs;
 

services/hydra/default.nix

@@ -1,4 +1,4 @@
-{ config, lib, ... }:
+{ config, lib, pkgs, ... }:
 
 let
   cfg = config.bagel.services.hydra;
@@ -47,6 +47,10 @@ in {
 
       notificationSender = "bagel@delroth.net";
 
+      # XXX: hydra overlay sets pkgs.hydra, but hydra's nixos module uses
+      # pkgs.hydra_unstable...
+      package = pkgs.hydra;
+
       buildMachinesFiles = [
         (pkgs.writeText "hydra-builders.conf" ''
           ssh://bagel-builder@epyc.infra.newtype.fr x86_64-linux ${config.age.secrets.hydra-ssh-key-priv.path} 8 1 big-parallel,kvm,nixos-test - c3NoLWVkMjU1MTkgQUFBQUMzTnphQzFsWkRJMU5URTVBQUFBSUJwcFBwKzhsdDFSTDNodW5aaGlXRUUvY1laaHJXYjFzaVhKVWpiU2l6Rzggcm9vdEBlcHljCg==