This adds support for the passthrough on build, push, login, and search.
Revamp the integration test to cover these cases and make it more
robust.
Use backticks instead of quoted strings for backslash-heavy string
contstands.
Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
Changes how the Engine interacts with Registry servers on image pull.
Previously, Engine sent a User-Agent string to the Registry server
that included only the Engine's version information. This commit
appends to that string the fields from the User-Agent sent by the
client (e.g., Compose) of the Engine. This allows Registry server
operators to understand what tools are actually generating pulls on
their registries.
Signed-off-by: Mike Goelzer <mgoelzer@docker.com>
