Run cargo machete in CI and on just lint.

.github/workflows/machete.yaml

@@ -0,0 +1,28 @@
+name: find unused dependencies
+
+on:
+  push:
+
+jobs:
+  cargo-machete:
+    name: find unused dependencies with cargo machete
+    runs-on: ubuntu-latest
+    env:
+      CARGO_NET_GIT_FETCH_WITH_CLI: "true"
+      RUSTFLAGS: "-D warnings" # fail on warnings
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: install tools
+        run: |
+          rustup show
+          cargo install cargo-machete
+
+      - uses: Swatinem/rust-cache@v2
+        with:
+          shared-key: "build" # share the cache across jobs
+          save-if: false
+
+      - name: find unused dependencies
+        run: |
+          cargo machete --with-metadata

.github/workflows/test.yaml

@@ -20,6 +20,7 @@ jobs:
       - uses: Swatinem/rust-cache@v2
         with:
           shared-key: "build" # share the cache across jobs
+          save-if: false
 
       - name: run tests
         run: cargo test --release --all-targets --all-features