`docker rename foo ''` would result in:
```
usage: docker rename OLD_NAME NEW_NAME
```
which is the old engine's way of return errors - yes that's in the
daemon code. So I fixed that error msg to just be normal.
While doing that I noticed that using an empty string for the
source container name failed but didn't print any error message at all.
This is because we would generate a URL like: ../containers//rename/..
which would cause a 301 redirect to ../containers/rename/..
however the CLI code doesn't actually deal with 301's - it just ignores
them and returns back to the CLI code/caller.
Rather than changing the CLI to deal with 3xx error codes, which would
probably be a good thing to do in a follow-on PR, for this immediate
issue I just added a cli-side check for empty strings for both old and
new names. This way we catch it even before we hit the daemon.
API callers will get a 404, assuming they follow the 301, for the
case of the src being empty, and the new error msg when the destination
is empty - so we should be good now.
Add tests for both cases too.
Signed-off-by: Doug Davis <dug@us.ibm.com>
Upstream-commit: 848792c42e61070adc4107a39d6a044e2ed615f7
Component: engine
3a09d2b95a