fix gce.conf multi-value parameter processing

cluster/gce/container-linux/configure-helper.sh

@@ -215,14 +215,19 @@ EOF
   if [[ -n "${NODE_INSTANCE_PREFIX:-}" ]]; then
     use_cloud_config="true"
     if [[ -n "${NODE_TAGS:-}" ]]; then
-      local -r node_tags="${NODE_TAGS}"
+      # split NODE_TAGS into an array by comma.
+      IFS=',' read -r -a node_tags <<< ${NODE_TAGS}
     else
       local -r node_tags="${NODE_INSTANCE_PREFIX}"
     fi
     cat <<EOF >>/etc/gce.conf
-node-tags = ${node_tags}
 node-instance-prefix = ${NODE_INSTANCE_PREFIX}
 EOF
+    for tag in ${node_tags[@]}; do
+      cat <<EOF >>/etc/gce.conf
+node-tags = ${tag}
+EOF
+    done
   fi
   if [[ -n "${MULTIZONE:-}" ]]; then
     use_cloud_config="true"
@@ -232,9 +237,13 @@ EOF
   fi
   if [[ -n "${GCE_ALPHA_FEATURES:-}" ]]; then
     use_cloud_config="true"
-    cat <<EOF >>/etc/gce.conf
-alpha-features = ${GCE_ALPHA_FEATURES}
+    # split GCE_ALPHA_FEATURES into an array by comma.
+    IFS=',' read -r -a alpha_features <<< ${GCE_ALPHA_FEATURES}
+    for feature in ${alpha_features[@]}; do
+      cat <<EOF >>/etc/gce.conf
+alpha-features = ${feature}
 EOF
+    done
   fi
   if [[ -n "${SECONDARY_RANGE_NAME:-}" ]]; then
     use_cloud_config="true"

cluster/gce/gci/configure-helper.sh

@@ -585,14 +585,19 @@ EOF
   if [[ -n "${NODE_INSTANCE_PREFIX:-}" ]]; then
     use_cloud_config="true"
     if [[ -n "${NODE_TAGS:-}" ]]; then
-      local -r node_tags="${NODE_TAGS}"
+      # split NODE_TAGS into an array by comma.
+      IFS=',' read -r -a node_tags <<< ${NODE_TAGS}
     else
       local -r node_tags="${NODE_INSTANCE_PREFIX}"
     fi
     cat <<EOF >>/etc/gce.conf
-node-tags = ${node_tags}
 node-instance-prefix = ${NODE_INSTANCE_PREFIX}
 EOF
+    for tag in ${node_tags[@]}; do
+      cat <<EOF >>/etc/gce.conf
+node-tags = ${tag}
+EOF
+    done
   fi
   if [[ -n "${MULTIZONE:-}" ]]; then
     use_cloud_config="true"
@@ -602,9 +607,13 @@ EOF
   fi
   if [[ -n "${GCE_ALPHA_FEATURES:-}" ]]; then
     use_cloud_config="true"
-    cat <<EOF >>/etc/gce.conf
-alpha-features = ${GCE_ALPHA_FEATURES}
+    # split GCE_ALPHA_FEATURES into an array by comma.
+    IFS=',' read -r -a alpha_features <<< ${GCE_ALPHA_FEATURES}
+    for feature in ${alpha_features[@]}; do
+      cat <<EOF >>/etc/gce.conf
+alpha-features = ${feature}
 EOF
+    done
   fi
   if [[ -n "${SECONDARY_RANGE_NAME:-}" ]]; then
     use_cloud_config="true"

pkg/cloudprovider/providers/gce/gce.go

@@ -149,6 +149,7 @@ type GCECloud struct {
 	AlphaFeatureGate *AlphaFeatureGate
 }
 
+// TODO: replace gcfg with json
 type ConfigGlobal struct {
 	TokenURL  string `gcfg:"token-url"`
 	TokenBody string `gcfg:"token-body"`
@@ -173,7 +174,7 @@ type ConfigGlobal struct {
 	// located in (i.e. where the controller will be running). If this is
 	// blank, then the local zone will be discovered via the metadata server.
 	LocalZone string `gcfg:"local-zone"`
-	// Possible values: List of api names separated by comma. Default to none.
+	// Default to none.
 	// For example: MyFeatureFlag
 	AlphaFeatures []string `gcfg:"alpha-features"`
 }