Docker 1.12 breaks "docker tag -f" in scripts

We have some scripts that run as part of our build that use docker tag to strip the name of our internal repository. They work fine, but our environment does not at all have consistent versions of Docker and isn’t 100% solid about cleaning itself up, so as originally written on Docker 1.old they used docker tag -f to maybe overwrite an existing tag. Around Docker 1.10 this started printing a scare warning that it was unnecessary; Docker 1.12 actually removed it.

I don’t necessarily have a problem with this changing, but can it be listed on

Relatedly, is there a good reliable way to determine the client program version that’s better than picking the third word out of docker --version? docker version -f {{.Client.Version}} would be perfect but doesn’t work on Docker 1.6, and the human-readable docker version output appears to have changed between 1.6 and 1.12.