building local RPM-based Docker images

[Colin Walters <walters verbum org>]

Hi all,

I have some software I'm working on that's RPM-based currently, and I'd 
like to *additionally* ship it as a Docker container (I need to 
maintain the ability to build/run it as an RPM as well).

Now a lot of the Dockerfiles one finds out there are are consuming 
existing packages, but in my case I have:

* A local git repository
* Some process to build git -> rpm (for the purposes now, let's say 
that's "fedpkg local", or "fedpkg mockbuild")

What's the best practice to do something like:

FROM fedora:20
ADD my.rpm /root/my.rpm
RUN yum -y localinstall /root/my.rm && rm -f /root/my.rpm

An annoying detail for example with the ADD command is that every time 
I do a build the version number changes (and thus the filename), and so 
I'd have to do something like:

ln -s myapp-4.3-1.fc21.x86_64.rpm myapp-latest.rpm 

I know there's
https://github.com/openshift/docker-source-to-images
would this be a case for that?  It feels like not since I'm building 
the RPM on the host system, not inside the Dockerfile.

Also, what I really want is to build *multiple* rpms locally, possibly 
with some dependent on others, and that leads more towards using yum 
repos for host -> container.

Has anyone else encountered this situation?