Manual smoke test: image cleanup

Verifies the opt-in image cleanup that runs after a successful, health-passed update (PLAN §5.2 step 8). Cleanup is off by default; it removes the image the replaced container was running, and is best-effort (a shared image still referenced by another container is kept, and a cleanup failure never fails the update).

There are two knobs:

• [settings] cleanup = true (or per container freshdock.cleanup=true): remove the replaced image after a healthy update.
• [settings] prune_dangling = true: additionally run a daemon-wide dangling-image prune after each successful update.

The unit tests in src/docker/recreate.rs (recreate_with_health_removes_old_image_when_cleanup_enabled, recreate_with_health_prunes_dangling_when_enabled, cleanup_failure_does_not_fail_the_update) are the authoritative checks; this procedure is for human verification against a real daemon.

Prerequisites

• A working Docker daemon on the standard socket.
• freshdock built locally: just build.

Steps

freshdock recreate always pulls the container’s tag before it recreates, so the tag has to exist upstream: a local-only tag such as fd-cleanup:demo fails the pull with a 404 before cleanup ever runs. The procedure therefore points the real nginx:alpine tag at an older image for the duration of the test. The container keeps that older image id, and the recreate’s own pull moves the tag back to the current upstream image, so the originally-running image is no longer referenced afterwards.

# 1. Point `nginx:alpine` at an older image and run a container on it with
#    cleanup opted in.
docker pull nginx:1.27-alpine
docker tag  nginx:1.27-alpine nginx:alpine

docker run -d --name fd-cleanup \
  --label freshdock.enable=true \
  --label freshdock.mode=watch \
  --label freshdock.cleanup=true \
  nginx:alpine
old_id=$(docker inspect fd-cleanup --format '{{.Image}}')

# 2. Drop the extra tag so nothing but the container references the old image.
#    Skip this step to exercise the shared-image guard instead (see below).
docker rmi nginx:1.27-alpine

# 3. Recreate. The pull restores the upstream `nginx:alpine`; after the new
#    container is healthy the superseded image is removed (best-effort).
./target/release/freshdock recreate fd-cleanup

# 4. The old image id must be gone (no container references it any more).
docker image inspect "$old_id" >/dev/null 2>&1 \
  && echo "FAIL: old image still present" \
  || echo "OK: superseded image removed"

Expected observations

• The CLI prints a line starting recreated fd-cleanup: healthy that names the removed archive and the new id.
• Step 4 prints OK: superseded image removed.
• With freshdock.cleanup=false (or the label omitted and [settings] cleanup unset), step 4 instead prints FAIL, i.e. the old image is kept. That is the correct default-off behaviour; re-run the procedure from step 1 without the cleanup label to confirm.
• Shared-image guard. Skip step 2 (or keep a second container running on $old_id) and the removal is refused by the daemon (HTTP 409) because the image is still referenced, logged as a warning, and the update still reports success. The image stays until the last reference is gone.

Cleanup

docker rm -f fd-cleanup $(docker ps -a --filter name=fd-cleanup-old- -q) 2>/dev/null
docker rmi nginx:1.27-alpine 2>/dev/null || true
docker pull nginx:alpine   # only needed if you skipped step 3