This Docker Registry release brings a new storage driver implementation to the
Docker Registry along with bug fixes, documentation enhancements and logging
improvements.

What’s new?

Google Cloud Storage Driver
The Registry now supports Google's reliable and fast network and storage
infrastructure for layer and manifest storage.

Read-only mode
Enables a Registry to serve only read requests, useful to maintain read
availability during unsafe administrative tasks.

Configurable hostname support
Allows the specification of an externally-reachable URL for the Registry.

Improved handling of environmental variables
Enables environment variables to be specified which are not part of the
configuration file.

Configurable file-existence and HTTP health checks
Allows administrators to easily disable a registry temporarily by placing a file
on the filesystem. Additionally a registry can be configured to check the
health of other services, such as notification endpoints.

Enable configurable HTTP headers to be set in responses
This feature is usable for Registry administrators to set response headers for
various uses cases including increased security.

Redirect Support in the Swift Driver
The Swift storage driver now supports generating download URLs in line with
other cloud storage drivers.

Gotchas

In order to support valid hostnames as name components, supporting repeated dash
was added. Additionally double underscore is now allowed as a separator to
loosen the restriction for previously supported names.