Add diff command to compare images
Add --target option to build command to specify target build stage
Add support for digests when specifying base images in FROM
Add support for global ARG substitution between stages
Change console logger to use ISO8601 time and color levels
Change default cache TTL from 7 days to 14 days
Fix skipping of SSL verification
Fix incorrect Dockerfile parsing when comments appear in quotes (issues/287)
Fix entrypoint to correctly wrap the entrypoint in "sh -c ..." in certain cases