nix(refactor): Move shell scripts to subdirectory nix/tools

nix/tools/style.nix

@@ -0,0 +1,68 @@
+{ black
+, buildToolbox
+, checkedShellScript
+, git
+, hlint
+, nixpkgs-fmt
+, shellcheck
+, silver-searcher
+, stylish-haskell
+}:
+let
+  style =
+    checkedShellScript
+      {
+        name = "postgrest-style";
+        docs = "Automatically format Haskell, Nix and Python files.";
+        inRootDir = true;
+      }
+      ''
+        # Format Nix files
+        ${nixpkgs-fmt}/bin/nixpkgs-fmt . > /dev/null 2> /dev/null
+
+        # Format Haskell files
+        # --vimgrep fixes a bug in ag: https://github.com/ggreer/the_silver_searcher/issues/753
+        ${silver-searcher}/bin/ag -l --vimgrep -g '\.l?hs$' . \
+          | xargs ${stylish-haskell}/bin/stylish-haskell -i
+
+        # Format Python files
+        ${black}/bin/black . 2> /dev/null
+      '';
+
+  # Script to check whether any uncommited changes result from postgrest-style
+  styleCheck =
+    checkedShellScript
+      {
+        name = "postgrest-style-check";
+        docs = "Check whether postgrest-style results in any uncommited changes.";
+        inRootDir = true;
+      }
+      ''
+        ${style}
+
+        ${git}/bin/git diff-index --exit-code HEAD -- '*.hs' '*.lhs' '*.nix'
+      '';
+
+  lint =
+    checkedShellScript
+      {
+        name = "postgrest-lint";
+        docs = "Lint all Haskell files and bash scripts.";
+        inRootDir = true;
+      }
+      ''
+        # Lint Haskell files
+        # --vimgrep fixes a bug in ag: https://github.com/ggreer/the_silver_searcher/issues/753
+        ${silver-searcher}/bin/ag -l --vimgrep -g '\.l?hs$' . \
+          | xargs ${hlint}/bin/hlint -X QuasiQuotes -X NoPatternSynonyms
+
+        # Lint bash scripts
+        ${shellcheck}/bin/shellcheck test/create_test_db test/memory-tests.sh test/with_tmp_db
+      '';
+
+in
+buildToolbox
+{
+  name = "postgrest-style";
+  tools = [ style styleCheck lint ];
+}