Add code duplication analysis to the dev workflow

.github/workflows/test.yaml

@@ -43,6 +43,9 @@ jobs:
           - python-version: '3.10'
             toxenv: typing
             os: ubuntu-latest
+          - python-version: '3.10'
+            toxenv: duplication
+            os: ubuntu-latest
           - python-version: '3.10'
             toxenv: minimal
             os: ubuntu-latest
@@ -63,6 +66,12 @@ jobs:
           python-version: ${{ matrix.python-version }}
           allow-prereleases: true
 
+      - name: Set up Node.js (for jscpd)
+        if: matrix.toxenv == 'duplication'
+        uses: actions/setup-node@v4
+        with:
+          node-version: '22'
+
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip wheel

.gitignore

@@ -10,6 +10,7 @@ build/
 dist/
 venvs/
 .DS_Store
+.tmp/
 
 # Produced by versioningit
 src/con_duct/_version.py

.jscpd.json

@@ -0,0 +1,26 @@
+{
+  "threshold": 0,
+  "reporters": ["console"],
+  "ignore": [
+    "**/node_modules/**",
+    "**/.git/**",
+    "**/.tox/**",
+    "**/.venv/**",
+    "**/venvs/**",
+    "**/__pycache__/**",
+    "**/*.egg-info/**",
+    "**/.eggs/**",
+    "**/.cache/**",
+    "**/.npm/**",
+    "**/.idea/**",
+    "**/.mypy_cache/**",
+    "**/.ruff_cache/**",
+    "**/.pytest_cache/**",
+    "**/.tmp/**",
+    "**/dist/**",
+    "**/build/**",
+    "**/CHANGELOG.md"
+  ],
+  "minTokens": 50,
+  "minLines": 5
+}