Print consistent help with options and commands

These commands now all output the same thing:

 - docker
 - docker help
 - docker --help
 - docker -h

Signed-off-by: Ben Firshman <ben@firshman.co.uk>
Add instructions on how to get help on commands

Signed-off-by: Ben Firshman <ben@firshman.co.uk>
Consolidate documentation for -H option

Signed-off-by: Ben Firshman <ben@firshman.co.uk>
Update libcontainer to 84ad9386a0240acb7475429a835

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>
Add daemon flag to specify public registry mirrors

Adds support for a --registry-mirror=scheme://<host>[:port]
daemon flag. The flag may be present multiple times. If
provided, mirrors are prepended to the list of endpoints used
for image pull. Note that only mirrors of the public
index.docker.io registry are supported, and image/tag resolution
is still performed via the official index.

Docker-DCO-1.1-Signed-off-by: Tim Smith <timbot@google.com> (github: timbot)
engine.Env: comments and tests for Get()

Signed-off-by: Vincent Batts <vbatts@redhat.com>
builder/parser/dumper: Handle newlines appropriately.

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
builder/parser: fix handling of empty strings as the only argument.

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
builder: Fix a small bug that could improperly cache.

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
builder: Fix entrypoint and cmd semantics in evaluator. Test c/o @cnf

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
evaluator: ensure entrypoint stays blank if set blank while CMD is set.

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
Do not populate path to prevent runconfig merge conflict; remove
autoConfig seeding of entrypoint.

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
move entrypoint integration-cli test for blank entrypoint to separate function

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
builder: Fix an error check being done at the wrong spot in run
dispatcher

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
Merge pull request #7984 from vbatts/vbatts-engine_env_comments

engine.Env: comments and tests for Get()
Merge pull request #7806 from erikh/fix_cmd_handling_in_parser

Fix cmd and entrypoint handling in parser
Merge pull request #7202 from timbot/add-registry-mirror-flag

Add daemon flag to specify public registry mirrors
Validate tag names similar to repository name validation; add tests
Addresses #7943

Docker-DCO-1.1-Signed-off-by: Phil Estes <estesp@linux.vnet.ibm.com> (github: estesp)
Merge pull request #7959 from crosbymichael/update-libcontainer-sep6

Update libcontainer to 84ad9386a0240acb7475429a835
Merge pull request #7996 from estesp/7943-validate-tagnames

Validate tag names similar to repository name validation; add tests