libdnf actions plugin: possibility to modify per-repository configuration

[t184256]

It is possible to output conf.<option_name>=<value> from .actions to alter DNF configuration, but it'd also be nice to be able to override repository configuration that way, similarly to how it was possible to, say,

for name, repo in self.base.repos.items():
    repo.<option_name> = <value>

Would probably also be useful to provide a ${repository_names} to iterate over.

[jmontleon]

I am using and was looking at what it would take to rewrite this plugin. It's pretty straightforward, but I think this is the functionality that's missing to make it possible.

https://github.com/michel-ludwig/dnf-local-mirror-detection/blob/master/src/local-mirror-detection.py

[jrohel]

@t184256
I prepared a PR #1539 which adds support for per-repository configuration modification.
Also adds ${conf.<repoid_pattern>.<option_name>[=<value_pattern>]} substitution. This is much more powerful than the proposed ${repository_names}.
More information in PR.

I'm also working on an even more flexible interface #1538 . But currently this work has a low priority.