Initial implementation of a Rebase command

This is a first iteration to implement Rebase. At the moment, this
does not implement --continue and --skip, so if the first
conflict is found, the only option is to --abort the command.

Bug: 328217
Change-Id: I24d60c0214e71e5572955f8261e10a42e9e95298
Signed-off-by: Mathias Kinzler <mathias.kinzler@sap.com>
Signed-off-by: Chris Aniszczyk <caniszczyk@gmail.com>
6 files changed