It's my first PR here, could someone tell what should I do?

@ChenLingPeng gofmt chekcs that a code format fits to the code style.
Please, run the gofmt -d -s . | grep -v Godeps/_workspace/src/ inside your fork to look at the diff, which fixes the style. And gofmt -s -w . | grep -v Godeps/_workspace/src/ to apply this fix to your code.

Thanks @noxiouz . Now it works!

From the specification:

For deletes, reference must be a digest or the delete will fail.

Because manifests have embedded the name and tag, deletions can only be done at the manifest level and only by digest. This is because, under concurrent load, the correct manifest to delete cannot be ascertained with certainty. The correct solution is to separate the tag from the manifest.

Please see #173 for a more complete proposal that would make tag deletion possible.

I don't feel this is the right approach to the API modifications. I'm closing this until we can get a proper proposal. Please use #174 and commentary from #62 as a template for how this should work.