Stage 1 · L05

Read Git history and Docker lifetimes without confusing them

Core · original Session 1 plus essential local Git/Docker setup

Git records a reviewable source history. Docker records a packaged runtime; its containers are disposable processes. Learn both boundaries before the database lessons. Copy the starter to a learner workspace, initialize a local Git repository, add a .gitignore excluding .venv, .env, caches and data volumes, and commit a passing baseline. Never commit a database URL or a real email/API key.

After implementing availability, inspect git diff before committing. The diff should show the one route body you intended to change, not an entire environment or unrelated files. git status tells you which files are tracked, changed or untracked. A commit stores source state; it does not publish the website, run a CI service, create a Docker image or back up PostgreSQL data.

A Docker image is the filesystem/configuration template. A container is one running instance with its own lifecycle. Stopping a container stops its process; removing it deletes its writable layer. A named volume can outlive that removal. Stage 02 introduces a database volume deliberately so data can survive an app restart. A successful container start is not proof that the application is ready or that a migration ran.

Run docker version to check the daemon, not only the CLI binary. The revision runner uses --pull never, an internal network, owned resource names and a disposable PostgreSQL tmpfs. That fixture's data is intentionally deleted when the check ends. It is useful for learning tests and unsuitable as a persistent development database. The Compose example in stage 02 has a separate learner volume and explicit loopback binding.

Keep this local setup here in the core path. Branch reconciliation, PR review, Black/Pylint hooks and hosted CI belong to the later quality supplement. The simple local commit exercise is not a claim that any remote repository settings, required checks or merge protections have been configured.

Cloning creates a local repository with history, a working tree and an origin reference. It does not install packages, activate a venv, run migrations or copy an existing database. Staging chooses the exact changes for the next commit; git diff --cached reviews that selection. A container port also needs two deliberate boundaries: the server listens on its container interface, while a host-published port can bind only to loopback. The test runner publishes no app port; its TCP check is inside the isolated container.

git init
git status
git diff
git add equipment/api.py
git diff --cached
# Commit only after the local baseline and transfer pass.
docker version

git diff shows unstaged edits; git diff --cached shows selected changes; a commit records the selected source revision. An image is a runtime template, a container is an instance, and a named volume has an independent lifetime. A source commit does not preserve that volume.

python run_checks.py --stage 01 --role starter --prepare
python run_checks.py --stage 01 --role starter
python run_checks.py --stage 01 --role starter --transfer

python run_checks.py --stage 01 --role solution --transfer

@router.get("/{equipment_id}/availability")
def availability(equipment_id: int):
    item = get_equipment(equipment_id)
    return {"equipment_id": item["id"], "available": item["quantity"]}