Add version-suffix to dependency channels

flake.lock

@@ -42,11 +42,11 @@
     },
     "emacs-overlay": {
       "locked": {
-        "lastModified": 1628819915,
-        "narHash": "sha256-Tez1lTYaHmSzPD2eiCjL3y/9CicBGV/vt9Q7N4oAbBI=",
+        "lastModified": 1628846943,
+        "narHash": "sha256-0jnjXLvNBBcR+tUZnFxdFjEHKgDeFTl7YGnz7qZUqfE=",
         "owner": "nix-community",
         "repo": "emacs-overlay",
-        "rev": "38361008b2444f25f1927e73d4ec524b93e2a5da",
+        "rev": "a0ca2c855f2f0a21a8b3989e8ceee6f2f823027e",
         "type": "github"
       },
       "original": {

flake.nix

@@ -37,8 +37,19 @@
       };
       hostDefaults = {
         modules = [
-          ({ lib, ... }: {
-            environment.etc = lib.mapAttrs' (key: val: { name = "channels/${key}"; value = { source = val.outPath; }; }) inputs;
+          ({ lib, pkgs, ... }: {
+            environment.etc = lib.mapAttrs'
+              (key: val: {
+                name = "channels/${key}";
+                value = {
+                  source = pkgs.runCommandNoCC "${key}-channel" { } ''
+                    mkdir $out
+                    echo "${val.rev or (toString val.lastModified)}" > $out/.version-suffix
+                    echo "import ${val.outPath}/default.nix" > $out/default.nix
+                  '';
+                };
+              })
+              inputs;
             nix.nixPath = [ "/etc/channels" ];
           })
           utils.nixosModules.saneFlakeDefaults