[cherry-pick] Update update-release-tracker.sh (#54)

/cherry-pick
Signed-off-by: Tamal Saha <tamal@appscode.com>

Co-authored-by: Tamal Saha <tamal@appscode.com>

Author: 1gtm

hack/scripts/update-release-tracker.sh

@@ -33,24 +33,30 @@ parse_url() {
     export RELEASE_TRACKER_PR=${PARTS[4]}
 }
 
-RELEASE_TRACKER=
+RELEASE_TRACKER=${RELEASE_TRACKER:-}
+GITHUB_BASE_REF=${GITHUB_BASE_REF:-}
 
 while IFS=$': \r\t' read -r -u9 marker v; do
     case $marker in
         Release-tracker)
-            export RELEASE_TRACKER=$v
+            export RELEASE_TRACKER=$(echo $v | tr -d '\r\t')
             ;;
         Release)
-            export RELEASE=$v
+            export RELEASE=$(echo $v | tr -d '\r\t')
             ;;
     esac
 done 9< <(git show -s --format=%b)
 
-[ ! -z $RELEASE_TRACKER ] || {
+[ ! -z "$RELEASE_TRACKER" ] || {
     echo "Release-tracker url not found."
     exit 0
 }
 
+[ ! -z "$GITHUB_BASE_REF" ] || {
+    echo "GitHub base ref not found."
+    exit 0
+}
+
 parse_url $RELEASE_TRACKER
 api_url="repos/${RELEASE_TRACKER_OWNER}/${RELEASE_TRACKER_REPO}/issues/${RELEASE_TRACKER_PR}/comments"