fix logic

update-gluon.sh

@@ -19,7 +19,7 @@ git remote add upstream "$gluon_upstream_git_url"
 git fetch upstream --tags
 
 # we already have this branch - exit
-if git rev-parse --verify "$fork_newest_minor_branch" &> /dev/null; then
+if ! git rev-parse --verify "$fork_newest_minor_branch" &> /dev/null; then
     echo "Nothing todo, branch $fork_newest_minor_branch already exists"
     exit 1
 fi