Bump nixpkgs to nixpkgs-unstable

Gives us fresher tooling and being able to move faster.

Author: domenkozar

default.nix

@@ -1,4 +1,4 @@
 let
   pkgs = import ./nix { };
 in
-pkgs.packages
+pkgs.packages // pkgs.checks

nix/default.nix

@@ -5,15 +5,39 @@
 let
   overlay =
     _: pkgs:
+    let
+      run = pkgs.callPackage ./run.nix { inherit tools; };
+      tools = pkgs.callPackage ./tools.nix { };
+    in
     {
       inherit (pkgs) nixfmt niv ormolu nixpkgs-fmt nix-linter;
-      cabal-fmt = pkgs.haskellPackages.cabal-fmt;
-      hindent = pkgs.haskellPackages.callCabal2nix "hindent" sources.hindent { };
-      packages = pkgs.callPackages ./packages.nix { };
+      cabal-fmt = pkgs.haskell.lib.enableSeparateBinOutput pkgs.haskellPackages.cabal-fmt;
+      hindent = pkgs.haskell.lib.enableSeparateBinOutput pkgs.haskellPackages.hindent;
+      inherit tools;
+      # Flake style attributes
+      packages = {
+        inherit tools run;
+        inherit (pkgs.gitAndTools) pre-commit;
+      };
+      checks = tools // {
+        # A pre-commit-check for nix-pre-commit itself
+        pre-commit-check = run {
+          src = ../.;
+          hooks = {
+            shellcheck.enable = true;
+            nixpkgs-fmt.enable = true;
+          };
+          excludes = [
+            # autogenerated by niv
+            "nix/sources.nix$"
+          ];
+        };
+      };
     };
 in
 import nixpkgs {
   overlays = [ overlay ];
-  config = { };
+  # broken is needed for hindent to build
+  config = { allowBroken = true; };
   inherit system;
 }

nix/packages.nix

@@ -11,28 +11,16 @@
         "url": "https://github.com/hercules-ci/gitignore/archive/2ced4519f865341adcb143c5d668f955a2cb997f.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
-    "hindent": {
-        "branch": "master",
-        "description": "Haskell pretty printer",
-        "homepage": null,
-        "owner": "chrisdone",
-        "repo": "hindent",
-        "rev": "a75d4033969ecf7d4d0a5eb985d3d1abb3b9301f",
-        "sha256": "0g9dm3mr7wi7bk55fvswv0zcw1khgyr2bmchrg6ks82jc9znxkr6",
-        "type": "tarball",
-        "url": "https://github.com/chrisdone/hindent/archive/a75d4033969ecf7d4d0a5eb985d3d1abb3b9301f.tar.gz",
-        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
-    },
     "nixpkgs": {
-        "branch": "release-20.09",
+        "branch": "master",
         "description": "A read-only mirror of NixOS/nixpkgs tracking the released channels. Send issues and PRs to",
         "homepage": "https://github.com/NixOS/nixpkgs",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "b60f5e90cf20d08be6b26177b50b44f2c6d653f5",
-        "sha256": "1pfk4gmsr1z3wz5f3crfy5r306d157ncqaidnmbrcjm812iy2baq",
+        "rev": "3be2b567425214cd7cab693a9820717d11b0bdac",
+        "sha256": "12kbh6fkyq703s1vcrypra7k844m8qnhz54ilqvldjap7hj1c57w",
         "type": "tarball",
-        "url": "https://github.com/NixOS/nixpkgs/archive/b60f5e90cf20d08be6b26177b50b44f2c6d653f5.tar.gz",
+        "url": "https://github.com/NixOS/nixpkgs/archive/3be2b567425214cd7cab693a9820717d11b0bdac.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     }
 }

nix/sources.json

@@ -16,7 +16,7 @@
 , nixfmt
 , nix-linter
 , callPackage
-, pythonPackages
+, python39Packages
 , rustfmt
 , clippy
 , cargo
@@ -26,10 +26,10 @@
 }:
 
 {
-  inherit ansible-lint hlint shellcheck ormolu hindent cabal-fmt nixpkgs-fmt nixfmt nix-linter rustfmt clippy cargo html-tidy;
+  inherit hlint shellcheck ormolu hindent cabal-fmt nixpkgs-fmt nixfmt nix-linter rustfmt clippy cargo html-tidy;
   inherit (elmPackages) elm-format;
   inherit (haskellPackages) stylish-haskell brittany hpack fourmolu;
-  inherit (pythonPackages) yamllint;
+  inherit (python39Packages) yamllint ansible-lint;
   inherit (nodePackages) prettier;
   purty = callPackage ./purty { purty = nodePackages.purty; };
   terraform-fmt = callPackage ./terraform-fmt { };