Merge pull request #29 from shizunge/parallel

Add `GANTRY_UPDATE_NUM_WORKERS` and other fixes

Misc cleanup

* Clarify uncessary commands.
* Update debug log on DOCKER_HOST.
* Do not set GANTRY_REGISTRY_HOST in tests.
* Load lib-common.sh st begining of tests.

[gantry] allow registries file to end without a newline.

It does not follow POSIX (https://stackoverflow.com/questions/729692/).
But it would be more user friendly.

Use ghcr.io latest release for image removal when no running as a doc…

…ker swarm service.

Some improvements on debug messages

Use ghcr.io latest release for image removal when no running as a doc…

…ker swarm service.

Some improvements on debug messages

output debug message in a better format.

do not remove untagged images. keep dev images for a week.

[entrypoint] use next run target time to calcualte the sleep time.

fix shellcheck

Merge pull request #4 from shizunge/dependabot/github_actions/docker/…

…setup-buildx-action-2.9.1

Bump docker/setup-buildx-action from 2.7.0 to 2.9.1