Deploy hooks

template/{% if layout == 'parts' %}README.md{% endif %}.jinja

@@ -11,4 +11,6 @@ make recreate
 
 `make env` creates `.env` from the examples of every part and copies each `docker-compose.override.yml.example`. `make recreate` starts the selected profiles, `make rebuild` builds the images first, `make logs`, `make restart` and `make down` do what they say.
 
+To deploy, `git pull && make deploy`. It runs `make pre-deploy` in every part, which builds images only when their inputs changed and applies migrations, then `docker compose up -d`, then `make post-deploy`, which restarts the services whose mounted code changed. A deploy system with its own `up` step calls the two hooks around it. What was built and started is remembered as `refs/deploy/*` in the clone.
+
 `make fmt`, `make check` and `make build` run in every part. Part-specific targets live in the part's own Makefile: `make -C {{ parts[0] }} ...`.