run cargo fmt as a nix derivation

.woodpecker/debug.yaml

@@ -14,7 +14,7 @@ steps:
   - name: check formatting
     image: nixpkgs/nix:nixos-24.05
     commands:
-      - nix-shell --attr devShell --run "cargo fmt -- --check"
+      - nix-build -j4 --attr flakePackages.fmt
 
   - name: build
     image: nixpkgs/nix:nixos-24.05

flake.nix

@@ -30,6 +30,10 @@
           inherit system nixpkgs crane rust-overlay extraTestEnv;
           release = false;
         }).garage-test;
+        lints = (compile {
+          inherit system nixpkgs crane rust-overlay;
+          release = false;
+        });
       in
       {
         packages = {
@@ -56,6 +60,10 @@
           tests-fjall = testWith {
             GARAGE_TEST_INTEGRATION_DB_ENGINE = "fjall";
           };
+
+          # lints (fmt, clippy)
+          fmt = lints.garage-cargo-fmt;
+          clippy = lints.garage-cargo-clippy;
         };
 
         # ---- developpment shell, for making native builds only ----

nix/compile.nix

@@ -190,4 +190,15 @@ in rec {
       pkgs.cacert
     ];
   } // extraTestEnv);
+
+  # ---- source code linting ----
+
+  garage-cargo-fmt = craneLib.cargoFmt (commonArgs // {
+    cargoExtraArgs = "";
+  });
+
+  garage-cargo-clippy = craneLib.cargoClippy (commonArgs // {
+    cargoArtifacts = garage-deps;
+    cargoClippyExtraArgs = "--all-targets -- -D warnings";
+  });
 }