[Update] Exit with fancy error when branch is empty

update.sh

@@ -26,15 +26,16 @@ DATE=$(date +%Y-%m-%d_%H_%M_%S)
 BRANCH=$(git rev-parse --abbrev-ref HEAD)
 
 function prefetch_images() {
-while read image; do
-  RET_C=0
-  until docker pull ${image}; do
-    RET_C=$((RET_C + 1))
-    echo -e "\e[33m\nError pulling $image, retrying...\e[0m"
-    [ ${RET_C} -gt 3 ] && { echo -e "\e[31m\nToo many failed retries, exiting\e[0m"; exit 1; }
-    sleep 1
-  done
-done < <(git show origin/${BRANCH}:docker-compose.yml | grep "image:" | awk '{ gsub("image:","", $3); print $2 }')
+  [[ -z ${BRANCH} ]] && { echo -e "\e[33m\nUnknown branch...\e[0m"; exit 1; }
+  while read image; do
+    RET_C=0
+    until docker pull ${image}; do
+      RET_C=$((RET_C + 1))
+      echo -e "\e[33m\nError pulling $image, retrying...\e[0m"
+      [ ${RET_C} -gt 3 ] && { echo -e "\e[31m\nToo many failed retries, exiting\e[0m"; exit 1; }
+      sleep 1
+    done
+  done < <(git show origin/${BRANCH}:docker-compose.yml | grep "image:" | awk '{ gsub("image:","", $3); print $2 }')
 }
 
 docker_garbage() {