fix: detect the right image name when there are many

get-modified-image.sh

 #!/bin/sh
 
-# retrieve the name of the image that was modified in the latest commit
+# retrieve the name and the version of the image that was modified in the latest commit
 # this script should become obsolete as soon as a proper way of getting the modified files is added to Gitlab CI
 
 RES=""
@@ -17,7 +17,7 @@ then
 	exit 1
 fi
 
-RES=$(cat $RES/docker-compose.yml | grep image: | head -n1 | cut -d ':' -f2-)
+RES=$(cat $RES/docker-compose.yml | grep $RES | cut -d ':' -f2-)
 if [[ "$RES" == "" ]]
 then
 	echo "No image modified"