Old solution causes amount of thread to be growing as well as stack is
increased during each iteration. Instead of cycle-free implementation,
this commit just uses while cycle
* allow to use one application for multiple repositories
* update tests
* handle None append argument everywhere
* rewrite repository definition logic
* drop optional flags from docs
* support of new schema in systemd units
* add migration docs and ability to migrate tree automatically
* use repostory id instead
* verbose multiarchitectureerror
* object path support for s3 sync
* fix tests after rebase
