Configure via container labels?

[cgwalters]

In #76 we talked about configuration a bit.

How about supporting configuration via labels? It feels really like a terrible hack to me to strcmp() the container's argv[0]. Something like:

LABEL org.projectatomic.systemd=yes
?
Then we could have:
LABEL org.projectatomic.systemd.journal=persistent
too?

[rhatdan]

I would not want to change what we have now, since it would break existing containers, but adding the second label would be fine with me.