Run the formatter in CI

Enable running formatter checks in CI. While we are at it add formatter
checks to the pre-commit hook.

Author: tcharding

.github/workflows/rust.yml

@@ -30,6 +30,10 @@ jobs:
         env:
           DO_DOCS: true
         run: ./contrib/test.sh
+      - name: Check formatting
+        env:
+          DO_FMT: true
+        run: ./contrib/test.sh
 
   Tests:
     name: Tests

contrib/test.sh

@@ -92,6 +92,15 @@ if [ "$DO_ASAN" = true ]; then
     cargo run --release --features=alloc --manifest-path=./no_std_test/Cargo.toml | grep -q "Verified alloc Successfully"
 fi
 
+# Run formatter if told to.
+if [ "$DO_FMT" = true ]; then
+    if [ "$NIGHTLY" = false ]; then
+        echo "DO_FMT requires a nightly toolchain (consider using RUSTUP_TOOLCHAIN)"
+        exit 1
+    fi
+    rustup component add rustfmt
+    cargo fmt --check
+fi
 
 # Bench if told to, only works with non-stable toolchain (nightly, beta).
 if [ "$DO_BENCH" = true ]

githooks/pre-commit

@@ -48,3 +48,6 @@ git diff-index --check --cached $against -- || exit 1
 
 # Check that code lints cleanly.
 cargo clippy --features=rand-std,recovery,lowmemory,global-context --all-targets -- -D warnings || exit 1
+
+# Check that the code formats correctly.
+cargo +nightly fmt --check || exit 1