handle changelog file in dist-git

[xsuchy]

See:
https://docs.pagure.org/Fedora-Infra.rpmautospec/principle.html

This means that if changelog file exists in dist-git, we should probably not touch it (there is already whitelist of files, which should not be touched).

Or alternatively, we can somehow work with it. But until this proposal mature, this is probably too soon.

[jmrodri]

Is tito often used for managing rpms in dist-git that are also updated directly in dist-git? In my typical use case, if I'm using tito I have it be the source of truth for the changelog etc. dist-git is merely a delivery mechanism. But I guess there are times where packages in dist-git go through rebuilds before the tito user can do another build.