add missing flag prefix --

new-deployable-site.sh

@@ -32,7 +32,7 @@ sudo bash -c "cat << EOF > ${my_repo}/hooks/post-receive
 mkdir -p '${my_deploy}'
 # always deploys from the default (master) branch
 git --work-tree='${my_deploy}' --git-dir='${my_repo}' checkout -f
-echo Deployed branch "'$(git rev-parse abbrev-ref HEAD)'" to '${my_deploy}'
+echo Deployed branch "'$(git rev-parse --abbrev-ref HEAD)'" to '${my_deploy}'
 EOF
 "