Depends on: (#42), #43

The process_distgit() function relies on the fact that the latest EVRs of the different distro versions are tagged in the dist-git repo of a package. Because we're starting "from scratch", it should ensure that this is the case before doing anything else.

Right now, process_distgit() lets users check if a package uses the auto features, or apply automatic release and changelog to a checked out dist-git repository.

Acceptance Criteria:

• The process-distgit command (and API) additionally tags latest EVR builds through rpmautospec.tag_package (needs to get a new action the user can choose on the command line/as function argument).
• The process_distgit_cb() callback needs to tag builds using the above, both in the local repository (for consumption by the command in the build root) and Pagure.