Added proposed Docker Community Guidelines

Docker-DCO-1.1-Signed-off-by: James Turnbull <james@lovedthanlost.net> (github: jamtur01)
Remove redundant checks in runconfig.Merge

Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)
Cleanup Cmd on ENTRYPOINT instruction

Fixes #5147
Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)
Inherit Cmd only if no --entrypoint specified on run

Fixes #5147
Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)
Rename DOCKER_CONFIG envvar to DOCKER_CERT_PATH

DOCKER_CONFIG was introduced in #6984.

We may use "config" for other purposes (e.g. #7232). Until we
have made a design decision around how configuration files will
work, DOCKER_CERT_PATH is a much safer name to rely on for future
compatibility.

Docker-DCO-1.1-Signed-off-by: Ben Firshman <ben@firshman.co.uk> (github: bfirsh)
Merge pull request #6909 from LK4D4/prune_cmd_on_entrypoint_setting_#5147

Cleanup cmd on entrypoint setting
Docker should use /var/lib/container/tmp for large temporary files.

/tmp is often a tmpfs file system and large temporary files could cause
docker commands to fail.  Also using /tmp potentially allows users on the
system to get access to content, or even attack the content.  Moving the tmpdir to
/var/lib/container/tmp will protect the data.

Docker-DCO-1.1-Signed-off-by: Dan Walsh <dwalsh@redhat.com> (github: rhatdan)

Conflicts:
	docker/docker.go
Merge pull request #7412 from bfirsh/rename-docker-config

Rename DOCKER_CONFIG envvar to DOCKER_CERT_PATH
Merge pull request #7186 from jamtur01/community

Added proposed Docker Community Guidelines
Merge pull request #6456 from rhatdan/tmpdir

Docker should use /var/lib/docker/tmp for large temporary files.
Save "COMMENT" field in Dockerfile into image content.

This will allow a user to save COMMENT data into an image, which
can later be retrieved using:

docker inspect IMAGEID

Copied the test example and some description data from Erik Hollensbe
<github@hollensbe.org>

Add support to allow docker import to populate Comment field

This patch also adds an option to docker import -m  Which will allow
base image builder to populate docker images with more comments then
just imported from FOOBAR.  This matches the docker commit -m functionality.

Docker-DCO-1.1-Signed-off-by: Dan Walsh <dwalsh@redhat.com> (github: rhatdan)

Docker-DCO-1.1-Signed-off-by: Dan Walsh <dwalsh@redhat.com> (github: rhatdan)

Conflicts:
	docs/sources/reference/builder.md