flake: move formatting and git hooks into dedicated modules

flake/dev/git-hooks.nix

@@ -0,0 +1,62 @@
+{ inputs, ... }:
+{
+  imports = [
+    inputs.git-hooks.flakeModule
+  ];
+
+  perSystem =
+    {
+      config,
+      pkgs,
+      system,
+      ...
+    }:
+    {
+      pre-commit = {
+        # We have a treefmt check already, so this is redundant.
+        # We also can't run the test if it includes running `nix build`,
+        # since the nix CLI can't build within a derivation builder.
+        check.enable = false;
+
+        settings.hooks = {
+          deadnix = {
+            enable = true;
+
+            settings = {
+              noLambdaArg = true;
+              noLambdaPatternNames = true;
+              edit = true;
+            };
+          };
+          treefmt = {
+            enable = true;
+            package = config.formatter;
+          };
+          typos = {
+            enable = true;
+            excludes = [ "generated/*" ];
+          };
+          maintainers = {
+            enable = true;
+            name = "maintainers";
+            description = "Check maintainers when it is modified.";
+            files = "^lib/maintainers[.]nix$";
+            package = pkgs.nix;
+            entry = "nix build --no-link --print-build-logs";
+            args = [ ".#checks.${system}.maintainers" ];
+            pass_filenames = false;
+          };
+          plugins-by-name = {
+            enable = true;
+            name = "plugins-by-name";
+            description = "Check `plugins/by-name` when it's modified.";
+            files = "^(?:tests/test-sources/)?plugins/by-name/";
+            package = pkgs.nix;
+            entry = "nix build --no-link --print-build-logs";
+            args = [ ".#checks.${system}.plugins-by-name" ];
+            pass_filenames = false;
+          };
+        };
+      };
+    };
+}