Feature Request: docker pull/push --calculate

[stampycode]

Currently there is no way to run a 'simulated' docker pull, and given the difference between layer hashes (used locally) and compressed layer hashes (used in the registries) it's not trivial to tell what the data cost will be to do a docker pull.

Please introduce a --calculate switch to the docker pull command to allow Docker to calculate the cost of a docker pull without actually doing one.

Similarly, a docker push --calculate would tell us how much data would be pushed to the registry without actually doing so, would be very useful for development when the user is bandwidth constrained.