RFE: Rsync -> new-sources -> commit -> push helper

[LecrisUT]

I have a situation where I want to update multiple packages from a repository that is linked to copr. Then I need to do those steps for each package on the list. I have automated these in a python script, but would also be nice if fbrnch can handle these or simplify the interface for doing these steps.

The missing interface are:

• fbrnch rsync from --staging-dir to --downstream-dir. Benefit is being able to provide multiple packages to be parallelized
• fbrnch new-sources: I think fbrnch update-sources would be equivalent, but couldn't get it to work