add flake

flake.lock

@@ -0,0 +1,25 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1694760568,
+        "narHash": "sha256-3G07BiXrp2YQKxdcdms22MUx6spc6A++MSePtatCYuI=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "46688f8eb5cd6f1298d873d4d2b9cf245e09e88e",
+        "type": "github"
+      },
+      "original": {
+        "id": "nixpkgs",
+        "type": "indirect"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

@@ -0,0 +1,25 @@
+{
+  description = "Get status information about multiple Git repositories";
+  outputs = { self, nixpkgs }@inputs:
+    let
+      forAllSystems = nixpkgs.lib.genAttrs nixpkgs.lib.platforms.unix;
+
+      nixpkgsFor = forAllSystems (system: import nixpkgs {
+        inherit system;
+      });
+    in
+      {
+        packages = forAllSystems (system:
+          let pkgs = nixpkgsFor.${system}; in
+          {
+            gis = pkgs.stdenv.mkDerivation {
+              name = "gis";
+              src = self;
+              installPhase = ''
+                install -m 755 -D gis $out/bin/gis
+              '';
+            };
+            default = self.packages.${system}.gis;
+        });
+      };
+}