diff --git a/plugin.sh b/plugin.sh
index 31e8cd3..bba5755 100755
--- a/plugin.sh
+++ b/plugin.sh
@@ -4,12 +4,12 @@ set -euo pipefail
 
 export PATH=$PATH:/kaniko/
 
-REGISTRY=${PLUGIN_REGISTRY:-index.docker.io}
+REGISTRY=${PLUGIN_REGISTRY:-docker.io}
 
 if [ "${PLUGIN_USERNAME:-}" ] || [ "${PLUGIN_PASSWORD:-}" ]; then
     DOCKER_AUTH=`echo -n "${PLUGIN_USERNAME}:${PLUGIN_PASSWORD}" | base64 | tr -d "\n"`
 
-    cat > /kaniko/.docker/config.json <<DOCKERJSON
+    cat > /kaniko/.docker/config.json <<EOF
 {
     "auths": {
         "${REGISTRY}": {
@@ -17,7 +17,7 @@ if [ "${PLUGIN_USERNAME:-}" ] || [ "${PLUGIN_PASSWORD:-}" ]; then
         }
     }
 }
-DOCKERJSON
+EOF
 fi
 
 if [ "${PLUGIN_JSON_KEY:-}" ];then
@@ -58,23 +58,24 @@ if [ -n "${PLUGIN_BUILD_ARGS_FROM_ENV:-}" ]; then
     BUILD_ARGS_FROM_ENV=$(echo "${PLUGIN_BUILD_ARGS_FROM_ENV}" | tr ',' '\n' | while read build_arg; do echo "--build-arg ${build_arg}=$(eval "echo \$$build_arg")"; done)
 fi
 
+# TODO: Test auto_tag behavior; potential bugs might still be here
 # auto_tag, if set auto_tag: true, auto generate .tags file
 # support format Major.Minor.Release or start with `v`
 # docker tags: Major, Major.Minor, Major.Minor.Release and latest
 if [[ "${PLUGIN_AUTO_TAG:-}" == "true" ]]; then
-    TAG=$(echo "${DRONE_TAG:-}" |sed 's/^v//g')
-    part=$(echo "${TAG}" |tr '.' '\n' |wc -l)
+    TAG=$(echo "${CI_COMMIT_TAG:-}" |sed 's/^v//g')
+    tag_part_count=$(echo "${TAG}" | tr '.' '\n' |wc -l)
     # expect number
-    echo ${TAG} |grep -E "[a-z-]" &>/dev/null && isNum=1 || isNum=0
+    echo ${TAG} | grep -E "[a-z-]" &>/dev/null && isNum=1 || isNum=0
 
-    if [ ! -n "${TAG:-}" ];then
+    if [ ! -n "${TAG:-}" ]; then
         echo "latest" > .tags
-    elif [ ${isNum} -eq 1 -o ${part} -gt 3 ];then
+    elif [ ${isNum} -eq 1 -o ${tag_part_count} -gt 3 ]; then
         echo "${TAG},latest" > .tags
     else
-        major=$(echo "${TAG}" |awk -F'.' '{print $1}')
-        minor=$(echo "${TAG}" |awk -F'.' '{print $2}')
-        release=$(echo "${TAG}" |awk -F'.' '{print $3}')
+        major=$(echo "${TAG}" | awk -F'.' '{print $1}')
+        minor=$(echo "${TAG}" | awk -F'.' '{print $2}')
+        release=$(echo "${TAG}" | awk -F'.' '{print $3}')
     
         major=${major:-0}
         minor=${minor:-0}