Initial implementation

.github/CODEOWNERS

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+* @heroku/languages

.github/dependabot.yml

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+version: 2
+updates:
+  - package-ecosystem: "cargo"
+    directory: "/"
+    schedule:
+      interval: "monthly"
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "monthly"

.github/workflows/check_changelog.yml

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+name: Check Changelog
+
+on:
+  pull_request:
+    types: [opened, reopened, labeled, unlabeled, synchronize]
+
+permissions:
+  contents: read
+
+jobs:
+  check-changelog:
+    runs-on: ubuntu-latest
+    if: |
+      !contains(github.event.pull_request.labels.*.name, 'skip changelog') &&
+      !contains(github.event.pull_request.labels.*.name, 'dependencies')
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+      - name: Check that CHANGELOG is touched
+        run: |
+          git fetch origin ${{ github.base_ref }} --depth 1 && \
+          git diff remotes/origin/${{ github.base_ref }} --name-only | grep CHANGELOG.md

.github/workflows/ci.yml

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+name: CI
+
+on:
+  push:
+    # Avoid duplicate builds on PRs.
+    branches:
+      - main
+  pull_request:
+
+permissions:
+  contents: read
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+      - name: Update Rust toolchain
+        run: rustup update
+      - name: Rust Cache
+        uses: Swatinem/rust-cache@v2.2.1
+      - name: Clippy
+        run: cargo clippy --all-targets --locked -- --deny warnings
+      - name: rustfmt
+        run: cargo fmt -- --check
+
+  unit-test:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+      - name: Update Rust toolchain
+        run: rustup update
+      - name: Rust Cache
+        uses: Swatinem/rust-cache@v2.2.1
+      - name: Run unit tests
+        run: cargo test --locked
+
+  integration-test:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        builder: ["builder:22", "buildpacks:20"]
+    env:
+      INTEGRATION_TEST_CNB_BUILDER: heroku/${{ matrix.builder }}
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+      - name: Install musl-tools
+        run: sudo apt-get install musl-tools --no-install-recommends
+      - name: Update Rust toolchain
+        run: rustup update
+      - name: Install Rust linux-musl target
+        run: rustup target add x86_64-unknown-linux-musl
+      - name: Rust Cache
+        uses: Swatinem/rust-cache@v2.2.1
+      - name: Install Pack CLI
+        uses: buildpacks/github-actions/setup-pack@v5.0.1
+      - name: Run integration tests
+        # Runs only tests annotated with the `ignore` attribute (which in this repo, are the integration tests).
+        run: cargo test --locked -- --ignored --test-threads 5

.github/workflows/release.yml

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+name: Release Buildpack
+
+on:
+  workflow_dispatch:
+
+permissions:
+  contents: write
+
+env:
+  BUILDPACK_DOCKER_REPO: docker.io/heroku/buildpack-python
+  CARGO_TERM_COLOR: always
+
+jobs:
+  # Releases the buildpack to Docker Hub and registers it with the CNB Buildpack Registry.
+  # This release process intentionally does not create a .cnb file release for now, since
+  # there are currently no use-cases that need it for Python.
+  release:
+    name: Release heroku/python
+    runs-on: ubuntu-latest
+    steps:
+      # Setup
+      - name: Checkout
+        uses: actions/checkout@v3
+      - name: Install musl-tools
+        run: sudo apt-get install musl-tools --no-install-recommends
+      - name: Update Rust toolchain
+        run: rustup update
+      - name: Install Rust linux-musl target
+        run: rustup target add x86_64-unknown-linux-musl
+      - name: Rust Cache
+        uses: Swatinem/rust-cache@v2.2.1
+      - name: Install libcnb-cargo
+        run: cargo install libcnb-cargo
+      - name: Install Pack CLI
+        uses: buildpacks/github-actions/setup-pack@v5.0.1
+      - name: Install yj and crane
+        uses: buildpacks/github-actions/setup-tools@v5.0.1
+      - name: Login to Docker Hub
+        uses: docker/login-action@v2
+        with:
+          registry: docker.io
+          username: ${{ secrets.DOCKER_HUB_USER }}
+          password: ${{ secrets.DOCKER_HUB_TOKEN }}
+
+      # Build
+      - name: Compile the buildpack
+        run: cargo libcnb package --release
+
+      # Publish
+      - name: Read buildpack metadata
+        run: |
+          echo "buildpack_id=$(yj -t < buildpack.toml | jq -r .buildpack.id)" >> $GITHUB_ENV
+          echo "buildpack_version=$(yj -t < buildpack.toml | jq -r .buildpack.version)" >> $GITHUB_ENV
+      - name: Check version is unique on Docker Hub
+        run: |
+          if docker manifest inspect "${{ env.BUILDPACK_DOCKER_REPO }}:${{ env.buildpack_version }}" > /dev/null; then
+            echo "Duplicate version found on Docker Hub ${{ env.BUILDPACK_DOCKER_REPO }}:${{ env.buildpack_version }}"
+            exit 1
+          fi
+      - name: Publish the buildpack to Docker Hub
+        run: pack buildpack package --path target/buildpack/release/heroku_python --publish "${{ env.BUILDPACK_DOCKER_REPO }}:${{ env.buildpack_version }}"
+      - name: Calculate the buildpack image digest
+        run: echo "buildpack_digest=$(crane digest ${{ env.BUILDPACK_DOCKER_REPO }}:${{ env.buildpack_version }})" >> $GITHUB_ENV
+      - name: Register the new version with the CNB Buildpack Registry
+        uses: docker://ghcr.io/buildpacks/actions/registry/request-add-entry:5.0.1
+        with:
+          token: ${{ secrets.CNB_REGISTRY_RELEASE_BOT_GITHUB_TOKEN }}
+          id: ${{ env.buildpack_id }}
+          version: ${{ env.buildpack_version }}
+          address: ${{ env.BUILDPACK_DOCKER_REPO }}@${{ env.buildpack_digest }}
+      - name: Create GitHub release
+        uses: actions/create-release@v1
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          tag_name: v${{ env.buildpack_version }}
+          release_name: v${{ env.buildpack_version }}
+          body: |
+            See the [CHANGELOG](./CHANGELOG.md) for details.
+          draft: false

.gitignore

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+__pycache__/
+target/
+.DS_Store

.vscode/extensions.json

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+{
+  "recommendations": ["rust-lang.rust-analyzer"],
+}

.vscode/settings.json

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+{
+  "rust-analyzer.check.command": "clippy",
+  "rust-analyzer.imports.granularity.enforce": true,
+  "rust-analyzer.imports.granularity.group": "module",
+  "rust-analyzer.imports.prefix": "crate",
+}

CHANGELOG.md

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+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+### Added
+
+- Initial implementation.