ci: Support incremental and nightly mutation testing

Author: Martin Taillefer

.github/workflows/main.yml

@@ -1,4 +1,5 @@
 name: main
+
 permissions:
   contents: read
   pull-requests: read
@@ -44,7 +45,7 @@ jobs:
       # prep
       - name: Checkout
         uses: actions/checkout@v6.0.0
-      - name: Start sscache
+      - name: Start sccache
         uses: mozilla-actions/sccache-action@v0.0.9
         with:
           version: ${{ env.SCCACHE_VERSION }}
@@ -87,7 +88,7 @@ jobs:
             ~/.cargo/registry/cache/
             ~/.cargo/git/db/
           key: ${{ runner.os }}-cargo-tools-${{ hashFiles('**/Cargo.lock') }}
-      - name: Start sscache
+      - name: Start sccache
         uses: mozilla-actions/sccache-action@v0.0.9
         with:
           version: ${{ env.SCCACHE_VERSION }}
@@ -161,7 +162,9 @@ jobs:
       # prep
       - name: Checkout
         uses: actions/checkout@v6.0.0
-      - name: Start sscache
+        with:
+          fetch-depth: 0
+      - name: Start sccache
         uses: mozilla-actions/sccache-action@v0.0.9
         with:
           version: ${{ env.SCCACHE_VERSION }}
@@ -176,11 +179,13 @@ jobs:
           tool: cargo-mutants@${{ env.CARGO_MUTANTS_VERSION }}
 
       # execute
-      - name: Mutate
+      - name: Generate PR diff
+        run: git diff origin/main...HEAD >diff.txt
+      - name: Mutate Diff
         env:
           DISABLE_T_REX: 1
         timeout-minutes: 45
-        run: cargo mutants --test-workspace=true --colors=never --jobs=1 --build-timeout=120
+        run: cargo mutants --test-workspace=true --colors=never --jobs=1 --build-timeout=120 --in-diff diff.txt
 
   coverage:
     if: github.event_name == 'pull_request'
@@ -196,7 +201,7 @@ jobs:
       # prep
       - name: Checkout
         uses: actions/checkout@v6.0.0
-      - name: Start sscache
+      - name: Start sccache
         uses: mozilla-actions/sccache-action@v0.0.9
         with:
           version: ${{ env.SCCACHE_VERSION }}

.github/workflows/nightly.yml

@@ -0,0 +1,85 @@
+name: nightly
+
+permissions:
+  contents: read
+  pull-requests: read
+  security-events: write
+
+on:
+  schedule:
+    - cron: '0 0 * * *'
+  workflow_dispatch:
+
+env:
+  CARGO_TERM_COLOR: always
+
+  # Rust toolchain versions
+  RUST_LATEST: "1.91"                                # used for mutation testing
+
+  # Tool versions
+  CARGO_MUTANTS_VERSION: "25.3.1"
+  SCCACHE_VERSION: "v0.12.0"
+
+jobs:
+  nightly-gatekeeper:
+    runs-on: ubuntu-latest
+    outputs:
+      should_skip: ${{ steps.check.outputs.should_skip }}
+    steps:
+      - uses: actions/checkout@v6.0.0
+        with:
+          fetch-depth: 0
+
+      - name: Check for changes in last 24 hours
+        id: check
+        run: |
+          # Check logs for commits in the last 24 hours on the current branch
+          if [[ -z $(git log --since="24 hours ago" --pretty=format:"%H") ]]; then
+            echo "No commits in the last 24 hours. Skipping..."
+            echo "should_skip=true" >> "$GITHUB_OUTPUT"
+          else
+            echo "New commits found. Proceeding..."
+            echo "should_skip=false" >> "$GITHUB_OUTPUT"
+          fi
+
+  mutation-testing:
+    needs: nightly-gatekeeper
+    if: ${{ needs.nightly-gatekeeper.outputs.should_skip != 'true' }}
+    runs-on: ubuntu-latest
+    env:
+      SCCACHE_GHA_ENABLED: "true"
+      RUSTC_WRAPPER: "sccache"
+    steps:
+      # prep
+      - name: Checkout
+        uses: actions/checkout@v6.0.0
+      - name: Start sccache
+        uses: mozilla-actions/sccache-action@v0.0.9
+        with:
+          version: ${{ env.SCCACHE_VERSION }}
+      - name: Install Rust
+        uses: actions-rust-lang/setup-rust-toolchain@v1.15.2
+        with:
+          toolchain: ${{ env.RUST_LATEST }}
+          components: clippy, rustfmt
+      - name: Install Cargo Tools
+        uses: taiki-e/install-action@v2.62.53
+        with:
+          tool: cargo-mutants@${{ env.CARGO_MUTANTS_VERSION }}
+
+      # execute
+      - name: Mutate All
+        env:
+          DISABLE_T_REX: 1
+        timeout-minutes: 90
+        run: cargo mutants --test-workspace=true --colors=never --jobs=1 --build-timeout=120
+
+      - name: Create Issue on Failure
+        if: failure()
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          gh issue create \
+            --title "🚨 Nightly Build Failed: $(date +'%Y-%m-%d')" \
+            --body "The nightly scheduled build failed. Please check the logs here: $GITHUB_SERVER_URL/$GITHUB_REPOSITORY/actions/runs/$GITHUB_RUN_ID" \
+            --label "bug"