Bump version: 21.14.0 → 21.14.1

Bump version: 21.13.0 → 21.14.0

Bump version: 21.12.0 → 21.13.0

Bump version: 21.11.0 → 21.12.0

Bump version: 21.10.2 → 21.11.0

- handle git and mercurial as source or target
- add argument to indicate target branch
- add argument to specify target version system
- when pushing a new branch, also try the ancestor branches too rather than update on tip (was done when pushing to mercurial)
- add argument to set commit message on duplicated repository

 fix running python3.6 unittests