--force: Propagate to shears.sh

After an annoying mistake and subsequent abort during a merging-rebase, I used the --force only to be stopped by a message from shears.sh telling me to use --force.

(As a side note, this commit could only have been made more amusing by submitting it yesterday...)
Merge pull request #199 from stuyvenberg/patch-1

--force: Propagate to shears.sh