Switch to flakes

Use VERSION file to define version for both Makefile and flake.nix.

.gitignore

@@ -23,3 +23,4 @@
 # End of https://www.gitignore.io/api/go
 /cmd/pistol/pistol
 /pistol
+result

Makefile

@@ -3,7 +3,7 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 NAME := pistol
-VERSION := v0.1.6
+VERSION := v$(shell cat VERSION)-git
 
 build:
 	go build -ldflags "-X 'main.Version=$(VERSION)'" ./cmd/pistol

VERSION

@@ -0,0 +1 @@
+0.1.6

default.nix

@@ -0,0 +1,9 @@
+(import (
+  let
+    lock = builtins.fromJSON (builtins.readFile ./flake.lock);
+  in fetchTarball {
+    url = "https://github.com/edolstra/flake-compat/archive/${lock.nodes.flake-compat.locked.rev}.tar.gz";
+    sha256 = lock.nodes.flake-compat.locked.narHash; }
+) {
+  src =  ./.;
+}).defaultNix

flake.nix

@@ -0,0 +1,40 @@
+{
+  description = "General purpose file previewer designed for Ranger, Lf to make scope.sh redundant";
+
+  # To make user overrides of the nixpkgs flake not take effect
+  inputs.nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+  inputs.flake-utils.url = "github:numtide/flake-utils";
+
+  # https://nixos.wiki/wiki/Flakes#Using_flakes_project_from_a_legacy_Nix
+  inputs.flake-compat = {
+    url = "github:edolstra/flake-compat";
+    flake = false;
+  };
+
+  outputs = { self, nixpkgs, flake-utils, flake-compat }:
+    flake-utils.lib.eachDefaultSystem
+      (system:
+        let
+          pkgs = nixpkgs.legacyPackages.${system};
+          pistol = pkgs.pistol.overrideAttrs(oldAttrs: rec {
+            version = "${builtins.readFile ./VERSION}-flake";
+            buildFlagsArray = [
+              "-ldflags=-s -w -X main.Version=${version}"
+            ];
+          });
+        in rec {
+          devShell = pkgs.mkShell {
+            buildInputs = pistol.buildInputs ++ [
+              pkgs.w3m
+            ];
+          };
+          packages.pistol = pistol;
+          defaultPackage = pistol;
+          apps.pistol = {
+            type = "app";
+            program = "${pistol}/bin/pistol";
+          };
+          defaultApp = apps.pistol;
+        }
+      );
+}