A container that keeps itself current
0.4.0 taught a board to update itself, but only when it ran from a git checkout; a Docker image had nothing to move and could only show the notice. Now it can follow releases too.
Set TSBB_CHECKOUT_DIR to a directory on the container's volume (/app/data/app, say). On first boot the container clones the repository there at the image's own commit and installs from the image's own package store, about three seconds with no download, and runs from that checkout. Each new release is then fetched into the volume and the server started again from it, within five minutes of it being published. A container restart comes back on the release the volume holds, not the image it was built from.
Without TSBB_CHECKOUT_DIR the image runs its own code exactly as before.
The image now carries git, the start command is sh bin/entrypoint.sh, and the Railway healthcheck window is 300 seconds.