replace dataflow with simpler Thread code, remove dataflow dependency
Remove Future models
Extract a Propagate model that installs the gem for us
Revert "Always checkout detached branches, we never want tracking branches in cached-copy."

--detach is not available on the installed version of git

This reverts commit 204e4e38c9b7f5ee078f2493c5d9dcf5e4f5afb1.

Conflicts:

	ChangeLog.md
Clean up local branches that might interfere with the checkout.

This hopefully prevents the problem where an old branch does
not get properly updated when checking out.
Merge branch 'master' into feature/systemu_to_session
extract extra logging from Formater to ExtraLogger