Feature Proposal: Copying activity indicator for docker cp command

[jeffabailey]

When running this command show an activity indicator.

docker cp

When running it could some sort of spinner like this.

https://www.shellscript.sh/tips/spinner/spinner.gif

If progress doesn't start or fails midstream the spinner would stop.

[maximillianfx]

Good point @jeffabailey! @thaJeztah what do you think about expanding this to Dockerfile instruction COPY too? If you wish, I can contribute whit this.

[jeffabailey]

Sure, I don't know the internals enough to make the greatest judgment call.

It sounds reasonable to me.