container-diff requires server side API v1.39

[morsedl]

Expected behavior

Not having to be on the bleeding age to use container-diff. Official docker-ce releases (stable and edge) are still on API v1.38. I suppose I could build from sources, but that's could be quite some effort only to discover that API 1.39 is actually required by container-diff. Is it?

Actual behavior

Container-diff fails because it is reporting API v1.39 to the server.

Information

• container-diff version: Version 0.12.0 - 10/1/18
• Operating system: debian stretch (amd64)

Steps to reproduce the behavior

# container-diff diff daemon://42bdaf9e6bc6 daemon://5772dc0624b7 --type=file
ERRO[0000] error retrieving image daemon://42bdaf9e6bc6: retrieving image from daemon: Error response from daemon: client version 1.39 is too new. Maximum supported API version is 1.38
error retrieving image daemon://5772dc0624b7: retrieving image from daemon: Error response from daemon: client version 1.39 is too new. Maximum supported API version is 1.38

[dlorenc]

It looks like something in the negotiation is failing. For now you can override with DOCKER_API_VERSION=1.38 as an environment variable, but we should auto detect this better.

[nkubala]

Hmm, yeah we should be trying to negotiate the API version before using the client/calling out to docker. I'll take a look