(nix): upgrade to flakes

flake.lock

@@ -0,0 +1,42 @@
+{
+  "nodes": {
+    "flake-utils": {
+      "locked": {
+        "lastModified": 1605370193,
+        "narHash": "sha256-YyMTf3URDL/otKdKgtoMChu4vfVL3vCMkRqpGifhUn0=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "5021eac20303a61fafe17224c087f5519baed54d",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1608633860,
+        "narHash": "sha256-AGJfdJCR5jfIt8PqGiENXRqhthrS3Gxy8Wzb3Z2GsS4=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "da1b28ab8f361fbe14dc539cd69ce1bfd015fd68",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

@@ -0,0 +1,28 @@
+{
+    description = "crdt-enc";
+
+    inputs = {
+        nixpkgs.url = github:NixOS/nixpkgs;
+        flake-utils.url = "github:numtide/flake-utils";
+    };
+
+    outputs = { self, flake-utils, nixpkgs }:
+        flake-utils.lib.eachDefaultSystem (system:
+            let
+                pkgs = import nixpkgs { inherit system; };
+            in {
+                devShell = pkgs.stdenv.mkDerivation {
+                    name = "crdt-enc";
+                    buildInputs = [
+                        pkgs.gpgme
+                        pkgs.libsodium
+
+                        pkgs.cargo
+                        pkgs.rustc
+                        pkgs.rustfmt
+                        pkgs.rust-analyzer
+                    ];
+                };
+            }
+        );
+}

shell.nix

@@ -1,15 +0,0 @@
-let
-    pkgs = import <nixpkgs> {};
-in
-    pkgs.stdenv.mkDerivation {
-        name = "crdt-enc";
-        buildInputs = [
-            pkgs.gpgme
-            pkgs.libsodium
-
-            pkgs.cargo
-            pkgs.rustc
-            pkgs.rustfmt
-            pkgs.rust-analyzer
-        ];
-    }