Improve the Shell code style.

tools/publish.sh

@@ -13,12 +13,12 @@ CATEGORIES=false
 TAGS=false
 LASTMOD=false
 
-WORK_DIR=$(dirname $(dirname $(realpath "$0")))
+WORK_DIR="$(dirname $(dirname $(realpath "$0")))"
 
 check_status() {
   local _change=$(git status . -s)
 
-  if [[ ! -z ${_change} ]]; then
+  if [[ ! -z $_change ]]; then
     echo "Warning: Commit the following changes first:"
     echo "$_change"
     exit 1
@@ -81,7 +81,7 @@ push() {
 
 main() {
 
-  cd $WORK_DIR
+  cd "$WORK_DIR"
 
   check_status