Use env variables

Is your feature request related to a problem? Please describe. In k8s it is convenient to have a scratch container with no shell. the migrate command has forced us to add busybox to our docker container which seem sub-optimal.

Describe the solution you'd like A mapping between cmdline args and suitably scoped env variables. In particular the -path and -database args.

Describe alternatives you've considered

Building a migration interface directly into our golang service was considered but ruled out because we want tok eep functioality separate in different containers.

Additional context Add any other context or screenshots about the feature request here.