hooks: declare nixpkgs-fmt pre-commit hook

.pre-commit-config.yaml

@@ -0,0 +1,5 @@
+repos:
+-   repo: https://github.com/nix-community/nixpkgs-fmt
+    rev: master
+    hooks:
+    -   id: nixpkgs-fmt

CONTRIBUTING.md

@@ -6,7 +6,9 @@ the `template` branch to provide a host of useful NixOS configurations available
 "out of the box". If you wish to contribute such an expression please follow
 these guidelines:
 
-* format your code with [`nixpkgs-fmt`][nixpkgs-fmt]
+* format your code with [`nixpkgs-fmt`][nixpkgs-fmt]. You can run the `hooks`
+  command inside the nix shell to install a pre-commit hook that does this
+  for you.
 * The commit message follows the same semantics as [nixpkgs][nixpkgs].
   * You can use a `#` symbol to specify ambiguities. For example,
   `develop#zsh: <rest of commit message>` would tell me that your updating the

pkgs/applications/blockchains/miningcore/deps.nix

@@ -6,7 +6,8 @@ let
       inherit sha256;
       url = "${nugetUrlBase}/${name}/${version}";
     };
-in [
+in
+[
 
   (fetchNuGet {
     name = "Microsoft.AspNetCore.App.Runtime.linux-x64";

shell.nix

@@ -37,6 +37,7 @@ pkgs.mkDevShell {
     nixos-install
     nixos-generate-config
     nixos-enter
+    pre-commit
   ];
 
   env = { inherit name; };
@@ -54,6 +55,11 @@ pkgs.mkDevShell {
       category = "main";
       package = flk;
     }
+    {
+      name = "hooks";
+      help = "install git hooks";
+      command = "pre-commit install";
+    }
     {
       name = "grip";
       help = python38Packages.grip.meta.description;