The reasons for that:
I want a data container which expose
/usr/local/bundlerwritable by user
with uid 1000, so that gems can be installed in ruby docker image by an user,
which in turn I want so that generating files from docker won't create
permissions problems when I mount my local development codebase in docker.
adding the dockerfile in my docker-compose rules makes the data container
be rebuild (thus flushed) at each
docker-compose build, so I want it as
an image on docker hub.