Add weekly cargo-mutants workflow

.cargo/mutants.toml

@@ -0,0 +1,27 @@
+additional_cargo_args = ["--all-features"]
+examine_globs = ["units/src/**/*.rs"]
+exclude_globs = [
+    "units/src/amount/verification.rs" # kani tests
+]
+exclude_re = [
+    "impl Debug",
+    "impl Arbitrary",
+    "impl Display",
+    ".*Error",
+    # --------------------------------------------Crate-specific exclusions--------------------------------------------
+    # Units
+    # src/amount/mod.rs
+    "parse_signed_to_satoshi", # Can't kill all mutants since there is no denomination smaller than Satoshi
+    "fmt_satoshi_in", # Related to formatting/display
+    "dec_width", # Replacing num /= 10 with num %=10 in a loop causes a timeout due to infinite loop
+    # src/fee_rate/serde.rs
+    "as_sat_per_kwu::opt::deserialize::<impl Visitor for VisitOpt>.*", # Replaces return value with Ok(Default::default()), which is the same as Ok(None)
+    "as_sat_per_vb_floor::opt::deserialize::<impl Visitor for VisitOpt>.*", # Replaces return value with Ok(Default::default()), which is the same as Ok(None)
+    "as_sat_per_vb_ceil::opt::deserialize::<impl Visitor for VisitOpt>.*", # Replaces return value with Ok(Default::default()), which is the same as Ok(None)
+    # src/amount/serde.rs
+    "as_sat::opt::deserialize::<impl Visitor for VisitOptAmt<X>>.*", # Replaces return value with Ok(Default::default()), which is the same as Ok(None)
+    "as_btc::opt::deserialize::<impl Visitor for VisitOptAmt<X>>.*", # Replaces return value with Ok(Default::default()), which is the same as Ok(None)
+    "as_str::opt::deserialize::<impl Visitor for VisitOptAmt<X>>.*", # Replaces return value with Ok(Default::default()), which is the same as Ok(None)
+    # src/locktime/relative.rs
+    "Time::to_consensus_u32" # It will replace | with ^, which will return the same value since the XOR is always taken against the u16 and an all-zero bitmask
+]

.github/workflows/cron-weekly-cargo-mutants.yml

@@ -0,0 +1,41 @@
+name: Weekly cargo-mutants
+on:
+  schedule:
+    - cron: "0 0 * * 0" # runs weekly on Sunday at 00:00
+  workflow_dispatch: # allows manual triggering
+jobs:
+  cargo-mutants:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: taiki-e/install-action@v2
+        with:
+          tool: cargo-mutants
+      - run: cargo mutants --in-place --no-shuffle
+      - uses: actions/upload-artifact@v4
+        if: always()
+        with:
+          name: mutants.out
+          path: mutants.out
+      - name: Check for new mutants
+        if: always()
+        run: |
+          if [ -s mutants.out/missed.txt ]; then
+            echo "New missed mutants found"
+            gh issue create \
+            --title "New Mutants Found" \
+            --body "$(cat <<EOF
+          Displaying up to the first 10 mutants:
+
+          $(head -n 10 mutants.out/missed.txt)
+
+          For the complete list, please check the [mutants.out artifact](https://github.com/${{ github.repository }}/actions/runs/${{ github.run_id }}).
+          EOF
+          )"
+            echo "create_issue=true" >> $GITHUB_ENV
+          else
+            echo "No new mutants found"
+            echo "create_issue=false" >> $GITHUB_ENV
+          fi
+    env:
+      GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

.gitignore

@@ -14,6 +14,7 @@ hashes/target
 
 # Test artifacts
 bitcoin/dep_test
+mutants.out*
 
 # Fuzz artifacts
 hfuzz_target