Write a wrapper to provide the data directory for the flake

This is mostly useful when running `nix run` outside the repository.

Author: ibbem

default.nix

@@ -19,8 +19,7 @@
       inherit system;
       buildGitHubPages = false;
     };
-in
-  pkgs.maven.buildMavenPackage rec {
+  demo = pkgs.maven.buildMavenPackage rec {
     pname = "DiffDetective-Demo";
     # The single source of truth for the version number is stored in `pom.xml`.
     # Hence, this XML file needs to be parsed to extract the current version.
@@ -61,6 +60,17 @@ in
       '';
     };
 
+    passthru = {
+      data-wrapper = pkgs.writeShellScriptBin "DiffDetective-Demo" ''
+        if ! [ -d data ]
+        then
+          cp -r ${src}/data .
+          chmod u+w -R data
+        fi
+        ${demo}/bin/DiffDetective-Demo
+      '';
+    };
+
     nativeBuildInputs = [pkgs.makeWrapper];
 
     postInstall = ''
@@ -72,4 +82,6 @@ in
     '';
 
     meta.mainProgram = "DiffDetective-Demo";
-  }
+  };
+in
+  demo

flake.nix

@@ -1,5 +1,6 @@
 {
-  outputs = inputs: {
-    packages.x86_64-linux.default = import inputs.self {system = "x86_64-linux";};
+  outputs = inputs: rec {
+      packages.x86_64-linux.default = packages.x86_64-linux.DiffDetective.data-wrapper;
+      packages.x86_64-linux.DiffDetective = import inputs.self {system = "x86_64-linux";};
   };
 }