Through the `DOCKER_CLI_MOUNTS` and `DOCKER_CLI_SHELL` env variables. Also
allows setting the dev container name through the `DOCKER_CLI_CONTAINER_NAME`
env var.
The motivation for allowing overriding the volume mounts is the same as for
moby/moby#37845, namely that I/O perf on native mounted
disks on non-Linux (notably Mac OS) is just terrible, thus making it a real
pain to develop: one has to choose between re-building the image after every
single change (eg to run a test) or just work directly inside the same
container (eg with vim, but even then one would have to re-configure their dev
container every time it gets destroyed - containers, after all, are not
supposed to be long-lived).
Allowing to override DOCKER_CLI_MOUNTS makes it easy for everyone
to decide what their volume/syncing strategy is; for example
one can choose to use [docker-sync](https://github.com/EugenMayer/docker-sync).
As for the shell, it's nice to be able to use bash instead of the more
bare-bones `ash` if preferred.
Finally, being able to name the container can come in handy for easier
scripting on the host.
This patch won't change anything for anyone who doesn't set these env variables
in their environment.
Signed-off-by: Jean Rouge <rougej+github@gmail.com>
