cc @docker/distribution-maintainers

The previous behavior violated the registry API spec.

This sounds reasonable to add to 1.8 but it looks like we're also adding some new logic in that Clear function. Is that necessary for the release?

As far as I know, it's not necessary. It's there because I'm updating distribution to the latest master. It would be possible to branch from the earlier revision and apply only the HTTP status code change, if that's something we want to consider.

It is not necessary, the client does not currently call Delete so the new logic should not be on any other call path.

Does anyone know why the tests are failing? I see failures like the following which don't have an obvious connection to updating the dependency:

FAIL: docker_cli_run_test.go:1325: DockerSuite.TestRunCopyVolumeUidGid

docker_cli_run_test.go:1341:
   c.Fatalf("Wrong /hello ownership: %s, expected dockerio:dockerio", out)
... Error: Wrong /hello ownership: 2015/07/25 04:16:19 error generating version 4 uuid, retrying: open /dev/urandom: operation not permitted
dockerio:dockerio, expected dockerio:dockerio

This error occurs when the UUID library is unable to get enough random bits due to entropy exhaustion open /dev/urandom: operation not permitted

@calavera IIRC this is a code path that the engine does not use (for the registry soft-delete feature), but I'll let @RichardScothern & @aaronlehmann confirm that this indeed has no effect.

Our CI is gone fishing. Otherwise LGTM!

Waiting from green tests.

failed on /dev/urandom... le sighhhh, but merging