Use ormolu from nixpkgs

default.nix

@@ -148,7 +148,7 @@ let
   niv-devshell = haskellPackages.shellFor {
     buildInputs = [
       pkgs.nixpkgs-fmt
-      pkgs.ormolu
+      pkgs.haskellPackages.ormolu
     ];
     packages = ps: [ ps.niv ];
     shellHook = ''

nix/default.nix

@@ -1,14 +1,9 @@
 { sources ? import ./sources.nix }:
-let
-  ormoluCompiler = "ghc865";
-in
 import sources.nixpkgs {
   overlays = [
     (_: pkgs: { inherit sources; })
     (_: pkgs: { nixpkgs-fmt = import pkgs.sources.nixpkgs-fmt {}; })
     (_: pkgs: { termtosvg = pkgs.callPackage ./termtosvg.nix {}; })
-    (import ./haskell-overlay.nix { inherit ormoluCompiler; })
-    (_: pkgs: { ormolu = pkgs.haskell.packages."${ormoluCompiler}".ormolu; })
   ];
   config = {};
 }

nix/haskell-overlay.nix

@@ -1,14 +0,0 @@
-{ ormoluCompiler }: self: super:
-
-let
-  ormolu = import super.sources.ormolu { pkgs = self; inherit ormoluCompiler; };
-in
-{
-  haskell = super.haskell // {
-    packages = super.haskell.packages // {
-      "${ormolu.ormoluCompiler}" = super.haskell.packages.${ormolu.ormoluCompiler}.override {
-        overrides = ormolu.ormoluOverlay;
-      };
-    };
-  };
-}

nix/sources.json

@@ -23,18 +23,6 @@
         "url": "https://github.com/nix-community/nixpkgs-fmt/archive/2a64f4b6a597d0d62004ffcec3ae4fd83cd1efc8.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
-    "ormolu": {
-        "branch": "master",
-        "description": "A formatter for Haskell source code",
-        "homepage": null,
-        "owner": "tweag",
-        "repo": "ormolu",
-        "rev": "22839ed74c9964578ae3b2af5c693f605ac8a687",
-        "sha256": "055z8p8kl80fr50crcvy2djk3qg2x34p8pa7kihxlcj9wrhsijyy",
-        "type": "tarball",
-        "url": "https://github.com/tweag/ormolu/archive/22839ed74c9964578ae3b2af5c693f605ac8a687.tar.gz",
-        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
-    },
     "termtosvg": {
         "branch": "develop",
         "description": "Record terminal sessions as SVG animations",

script/fmt

@@ -1,12 +1,11 @@
 #!/usr/bin/env bash
 ###
-### fmt — find changed Haskell files and format them with ormolu
+### fmt - find changed Haskell files and format them with ormolu
 ###
 ### Usage:
-###   fmt [-c] [-i]
+###   fmt [-c]
 ###
 ### Options:
-###   -i        Format files inplace, will change files!
 ###   -c        Only check formatting, don't change files
 ###   -h        Print this message