By default we do not update a repository if the desired refspec is
already checked out and so we do not pull any new commits that may have
been added to this refspec upstream. If the new `--update` argument is
passed on the command line then we instead pull in any new upstream
commits.
Signed-off-by: Paul Barker <pbarker@konsulko.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>