holy moly we're almost there

shell/hooks/default.nix

@@ -0,0 +1,4 @@
+{
+  enable = true;
+  pre-commit.text = builtins.readFile ./pre-commit.sh;
+}

shell/hooks/pre-commit.sh

@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+
+if git rev-parse --verify HEAD >/dev/null 2>&1
+then
+  against=HEAD
+else
+  # Initial commit: diff against an empty tree object
+  against=$(${git}/bin/git hash-object -t tree /dev/null)
+fi
+
+diff="git diff-index --name-only --cached $against --diff-filter d"
+
+nix_files=($($diff -- '*.nix'))
+all_files=($($diff))
+
+# Format staged nix files.
+if [[ -n "${nix_files[@]}" ]]; then
+  nixpkgs-fmt "${nix_files[@]}" \
+  && git add "${nix_files[@]}"
+fi
+
+# check editorconfig
+editorconfig-checker -- "${all_files[@]}"
+if [[ $? != '0' ]]; then
+  printf "%b\n" \
+    "\nCode is not aligned with .editorconfig" \
+    "Review the output and commit your fixes" >&2
+  exit 1
+fi