The plugin allows the use of one set of credentials per-job, which works fine as long as we rely on images already present on the machine, but fails when the Dockerfile refers to a baseimage from a different (private) repository.

Example:
We setup a job with hello as the repo name and https://private-dev.repo.com/v2/ as the repo URL.
The content of the Dockerfile is:

FROM private-prod.repo.com/baseimage
RUN echo hello

Docker Build and Publish does not pull the image from the repo indicated in the FROM directive, because it comes from a different repository than the one defined as the target.

It should be possible to use multiple credentials per job, or at least to honor the ones inside the .dockercfg file.