Add rpm spec %config support

[bgaudaen]

Some feature addition...

[Mousius]

Hi @bgaudaen, could you give an example of your use case?

Also, there's been a lot of changes in master recently, so it'd be great if you're still interested to resolve the merge conflicts 😸

[bgaudaen]

Hi @DaMouse404, Just merged the changes.

My use case is the following:
I have an app which needs some configuration that is environment specific. Basically my RPM ships with a default configuration file "config.js" that will be edited after it is deployed. The default behaviour when you update the package is that this configuration file will be replaced by the one coming from the update. This is not what I want. What I want is to keep local changes on that file on the package update.
This is what the SPEC '%config' flag can do for me. Here is some more detailed documentation on the flag:
http://people.ds.cam.ac.uk/jw35/docs/rpm_config.html
http://rpm-guide.readthedocs.io/en/latest/appendix.html?highlight=noreplace#files