output git reset --hard $sha1
test "a$1" = a-n && output git reset --soft $current_sha1
sha1=$(git rev-parse --short $sha1)
output warn Fast forward to $sha1
else
output git reset --hard $sha1
test "a$1" = a-n && output git reset --soft $current_sha1
sha1=$(git rev-parse --short $sha1)
output warn Fast forward to $sha1
else