update-scripts/version-info: convert to a script

This will allow us to do impure things if needed.

update-scripts/update.nix

@@ -43,7 +43,7 @@ writeShellApplication {
 
     versionInfo() {
       nix-build ./update-scripts -A version-info
-      install -m 644 -T "$(realpath result)" ./version-info.toml
+      ./result
       if [ -n "$commit" ]; then
         git add version-info.toml
         git commit "$@"

update-scripts/version-info/default.nix

@@ -1,36 +1,20 @@
 {
   lib,
-  writers,
-  runCommand,
+  callPackage,
+  writeShellApplication,
 }:
 let
-  inherit (builtins)
-    all
-    match
-    attrNames
-    ;
-  inherit (lib)
-    importJSON
-    ;
-
-  lockFile = importJSON ../../flake.lock;
-  nixpkgsLock =
-    # Assert there is only one nixpkgs node
-    assert all (node: match "nixpkgs_[0-9]+" node == null) (attrNames lockFile.nodes);
-    lockFile.nodes.nixpkgs.original;
-
-  info = {
-    inherit (lib.trivial) release;
-    nixpkgs_rev = lib.trivial.revisionWithDefault (throw "nixpkgs revision not available");
-    unstable = lib.strings.hasSuffix "-unstable" nixpkgsLock.ref;
-  };
+  mainInfo = callPackage ./main.nix { };
 in
-runCommand "version-info.toml" { } ''
-  (
-    echo "# DO NOT MODIFY!"
-    echo "# This file was generated by ${
-      lib.strings.removePrefix (toString ../.. + "/") (toString ./default.nix)
-    }"
-    cat ${writers.writeTOML "version-info.toml" info}
-  ) > $out
-''
+writeShellApplication {
+  name = "version-info";
+  text = ''
+    (
+      echo "# DO NOT MODIFY!"
+      echo "# This file was generated by ${
+        lib.strings.removePrefix (toString ../.. + "/") (toString ./default.nix)
+      }"
+      cat ${mainInfo}
+    ) > version-info.toml
+  '';
+}

update-scripts/version-info/main.nix

@@ -0,0 +1,27 @@
+{
+  lib,
+  writers,
+}:
+let
+  inherit (builtins)
+    all
+    match
+    attrNames
+    ;
+  inherit (lib)
+    importJSON
+    ;
+
+  lockFile = importJSON ../../flake.lock;
+  nixpkgsLock =
+    # Assert there is only one nixpkgs node
+    assert all (node: match "nixpkgs_[0-9]+" node == null) (attrNames lockFile.nodes);
+    lockFile.nodes.nixpkgs.original;
+
+  info = {
+    inherit (lib.trivial) release;
+    nixpkgs_rev = lib.trivial.revisionWithDefault (throw "nixpkgs revision not available");
+    unstable = lib.strings.hasSuffix "-unstable" nixpkgsLock.ref;
+  };
+in
+writers.writeTOML "version-info.toml" info