fix(docker): ship git so the image can scaffold templates

.github/workflows/smoke-distribution.yml

@@ -65,6 +65,25 @@ jobs:
  test -s /tmp/cpa-help.txt
  python3 -c "from pathlib import Path; print('\n'.join(Path('/tmp/cpa-help.txt').read_text().splitlines()[:5]))"
 
+ # Image must ship git so template/extension clones work (see #219).
+ - name: Verify scaffold smoke
+ run: |
+ set -euo pipefail
+ mkdir -p /tmp/cpa-docker-smoke
+ docker run --rm \
+ -e CI=true \
+ -v /tmp/cpa-docker-smoke:/out \
+ -w /out \
+ "$DOCKER_IMAGE:latest" \
+ --template fastapi-starter \
+ --addons github-setup \
+ --no-interactive \
+ --no-install \
+ --refresh always \
+ /out/app
+ test -d /tmp/cpa-docker-smoke/app/.github/workflows
+ test -d /tmp/cpa-docker-smoke/app/app
+
  homebrew:
  name: Homebrew (Create-Python-App/tap)
  runs-on: macos-latest

Dockerfile

@@ -6,6 +6,12 @@ FROM python:3.12-slim-bookworm
 # reproducible for its tag).
 ARG VERSION=latest
 
+# git is required to clone cpa-templates (see #219).
+# hadolint ignore=DL3008
+RUN apt-get update \
+ && apt-get install -y --no-install-recommends git ca-certificates \
+ && rm -rf /var/lib/apt/lists/*
+
 # Retry pip install: PyPI simple-index / CDN edges can lag the JSON API
 # that CI already observed as ready (see #217).
 # hadolint ignore=DL3013