nixos/nix: add nix-diff

default.nix

@@ -13,7 +13,8 @@ let
   storePathLength = builtins.stringLength (builtins.toString builtins.storeDir);
   evaluatingInStore = (builtins.substring 0 storePathLength currentFilePath) == builtins.storeDir;
 
-  selfInStore = builtins.path {
+  gitlessSelfInStore = {
+    outPath = builtins.path {
       path = ./.;
       name = "source";
       filter = path: type:
@@ -26,6 +27,19 @@ let
             && lib.runGitignoreFilter gitIgnoreFilters path type;
         in result;
     };
+    selfMode = "path";
+  };
+  gitfullSelfInStore = builtins.fetchGit "file://${builtins.toString ./.}" // {
+    selfMode = "git";
+  };
+
+  selfInStore' = builtins.tryEval gitfullSelfInStore;
+  selfInStore = if selfInStore'.success then selfInStore'.value else gitlessSelfInStore;
 in
-if !(evaluatingInStore) then { ... }@args: import selfInStore ({ selfPath = selfInStore; } // args )
+if !(evaluatingInStore) then { ... }@args: import selfInStore ({
+  selfPath = {
+    outPath = builtins.toString ./.;
+    selfMode = "store";
+  };
+} // args )
 else { ... }@args: import ./outputs.nix ({ selfPath = selfInStore; } // args)

nix-os/nix.nix

@@ -54,6 +54,7 @@ in {
     nix.package = wrappedNixExecutables false;
     environment.systemPackages = [
       pkgs.nix-output-monitor
+      pkgs.nix-diff
     ] ++ lib.map (lib.hiPrio) [
       (wrappedNixExecutables true)
       wrappedNixosExecutables

outputs.nix

@@ -1,7 +1,10 @@
 {
   inputsPath ? ./inputs.nix,
   inputs ? import inputsPath {},
-  selfPath ? builtins.toString ./.,
+  selfPath ? {
+    outPath = builtins.toString ./.;
+    selfMode = "impure";
+  },
 }:
 
 let