Add SentinelCommit: a Claude-powered semantic pre-commit guardrail

.gitattributes

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+# Normalise text in the repository, let Git pick the working-copy ending.
+* text=auto
+
+# Shell scripts and Git hooks MUST keep LF endings. A hook checked out with
+# CRLF fails at exec time with "bad interpreter: /bin/sh^M", including under
+# Git for Windows and WSL.
+*.sh            text eol=lf
+hooks/pre-commit text eol=lf
+
+# Python stays LF for consistency across platforms.
+*.py            text eol=lf
+
+# Documentation.
+*.md            text

.github/workflows/ci.yml

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+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+jobs:
+  test:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, windows-latest]
+        python-version: ["3.10", "3.12"]
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+
+      - name: Install dependencies
+        run: pip install -r requirements.txt
+
+      - name: Unit tests
+        run: python -m unittest discover -s tests -v
+
+      - name: Hook must fail open without credentials
+        shell: bash
+        env:
+          ANTHROPIC_API_KEY: ""
+        run: |
+          # No key configured: the engine must allow the commit, not block it.
+          git config user.email ci@example.com
+          git config user.name CI
+          cp examples/transaction_fault_unsafe.py payment_service.py
+          git add payment_service.py
+          python sentinel.py
+          echo "exit=$? (0 required: fail open)"
+
+      - name: Mock verdict drives both demo scenarios
+        shell: bash
+        env:
+          SENTINEL_MOCK: "1"
+        run: |
+          git reset
+          cp examples/transaction_fault_unsafe.py payment_service.py
+          git add payment_service.py
+          if python sentinel.py; then
+            echo "::error::unsafe diff was not blocked"; exit 1
+          fi
+          git reset
+          cp examples/transaction_fault_safe.py payment_service.py
+          git add payment_service.py
+          python sentinel.py || { echo "::error::safe diff was blocked"; exit 1; }

.gitignore

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+# Python
+__pycache__/
+*.py[cod]
+*.egg-info/
+.pytest_cache/
+
+# Virtual environments
+venv/
+.venv/
+env/
+
+# Secrets - never commit an API key
+.env
+.env.*
+!.env.example
+
+# Editors / OS
+.vscode/
+.idea/
+.DS_Store
+Thumbs.db

LICENSE

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+MIT License
+
+Copyright (c) 2026 SentinelCommit contributors
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.