Isolate the dev-only flake inputs to improve performance

.github/workflows/update-data.yml

@@ -4,6 +4,9 @@ on:
   schedule:
     - cron: '0 15 * * 1'
   workflow_dispatch:
+  pull_request:
+    paths:
+      - dev/**
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}

dev/flake-module.nix

@@ -0,0 +1,60 @@
+{ inputs, ... }:
+{
+  perSystem =
+    {
+      system,
+      pkgs,
+      self',
+      lib,
+      ...
+    }:
+    let
+      emacsPackages = inputs.emacs-ci.packages.${system};
+    in
+    {
+      _module.args.pkgs = inputs.nixpkgs.legacyPackages.${system}.extend inputs.twist.overlays.default;
+
+      devShells = {
+        default = pkgs.mkShell { buildInputs = [ pkgs.just ]; };
+      };
+
+      packages = {
+        default = pkgs.linkFarm "default" (
+          [
+            {
+              name = "default.nix";
+              path = pkgs.writeText "emacs-builtins-default-nix" ''{${
+                lib.concatMapStrings (name: "${name} = import ./${name}.nix;\n") (builtins.attrNames emacsPackages)
+              }}'';
+            }
+          ]
+          ++ (lib.mapAttrsToList (emacsName: emacsPackage: {
+            name = "${emacsName}.nix";
+            path =
+              pkgs.runCommand "build-${emacsName}-builtins-nix"
+                {
+                  buildInputs = [ emacsPackage ];
+                }
+                ''
+                  EMACS_VERSION="$(emacs --version \
+                    | grep -F "GNU Emacs" \
+                    | grep -oE "[[:digit:]]+(:?\.[[:digit:]]+)+")"
+                  echo >>$out '{'
+                  echo >>$out "  version = \"''${EMACS_VERSION}\";"
+                  echo >>$out '  libraries = ['
+                  sed -e 's/^/"/' -e 's/$/"/' ${
+                    (pkgs.emacsTwist {
+                      inherit emacsPackage;
+                      initFiles = [ ];
+                      lockDir = null;
+                      inventories = [ ];
+                    }).builtinLibraryList
+                  } >>$out
+                  echo >>$out '  ];'
+                  echo >>$out '}'
+                '';
+          }) emacsPackages)
+        );
+      };
+    };
+}