ci: add GitHub Actions workflow and Codecov integration

.github/workflows/ci.yml

@@ -0,0 +1,62 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  fmt:
+    name: Formatting
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          components: rustfmt
+      - run: cargo fmt -- --check
+
+  clippy:
+    name: Clippy
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          components: clippy
+      - uses: Swatinem/rust-cache@v2
+      - run: cargo clippy --all-targets --all-features -- -D warnings
+
+  test:
+    name: Tests
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: Swatinem/rust-cache@v2
+      - run: cargo test --all-features
+
+  coverage:
+    name: Coverage
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          components: llvm-tools-preview
+      - uses: Swatinem/rust-cache@v2
+      - name: Install cargo-llvm-cov
+        uses: taiki-e/install-action@cargo-llvm-cov
+      - name: Generate coverage
+        run: cargo llvm-cov --all-features --lcov --output-path lcov.info
+      - name: Print coverage summary
+        run: cargo llvm-cov report --summary-only
+      - name: Upload to Codecov
+        uses: codecov/codecov-action@v5
+        with:
+          files: lcov.info
+          fail_ci_if_error: false
+          # token: ${{ secrets.CODECOV_TOKEN }}  # required for private repos

README.md

@@ -1,5 +1,8 @@
 # tiny-mb
 
+[![CI](https://github.com/mattwend/tiny-mb/actions/workflows/ci.yml/badge.svg)](https://github.com/mattwend/tiny-mb/actions/workflows/ci.yml)
+[![codecov](https://codecov.io/gh/mattwend/tiny-mb/branch/main/graph/badge.svg)](https://codecov.io/gh/mattwend/tiny-mb)
+
 Small Rust Modbus library with typed request/response PDUs and a reusable Modbus TCP transport.
 
 ## Features

codecov.yml

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+codecov:
+  require_ci_to_pass: true
+
+coverage:
+  precision: 2
+  round: nearest
+  range: 0...100
+
+  status:
+    project:
+      default:
+        target: auto
+        threshold: 1%
+    patch:
+      default:
+        target: auto
+        threshold: 1%
+
+comment:
+  layout: "diff, flags, files"
+  behavior: default
+  require_changes: false