Add death routines to git sibling

dotfiles/gittum/bin/sibling

 ## funz
 #
 
+die() {
+    echo "$@" 1>&2
+    exit 1
+}
+
+usage() {
+    echo "usage: git $(basename $0) NEWPROJ [TEMPLATE]"
+    exit 0
+}
+
 rewrite_uri_to () {
     # create a new remote URI based on current one
     git remote -v \
 #
 
 project=$1
+test -n "$project" || usage
 
 if [ -f $sibling_conf ];
 then