Comment 0 for bug 1722552

list of containers to promote should be taken dynamically

At the moment, the list of containers to promote is written on a static txt file, downloaded manually from a container build job run.
We should fetch the list of containers dynamically, inspecting the logs of the last passed container build job that use the hash we're promoting.
This needs modifications to the promoter script and the container push script, possible mainly after implementing the two other cards https://trello.com/c/OFCAG1ue and https://trello.com/c/50k8DmyT
And we also need to ensure such a list is written in the containers build job, since change https://review.rdoproject.org/r/9328 is removing the creation of such file

Promoter script configuration file should implement subsections

Promoter script would need at least:
- verbose mode, right now it logs only on a file
- extend dry_run to containers and qcow promotion

Improve promoter script debugging

INI files usually contain sections, keys and value. This is somewhat limiting, and in the promoter script for example, known sections are removed, so that the remaining sections can all be considered tags names.
We should use subsections instead, which are not in the standard configparser implementation, but are easy to implement, and render the configuration more extendable.
Ex.
[main]
user:

[promote_from:tripleo-ci-testing]
current-tripleo

[jobs_required:current-tripleo]
job1
job2
job3