split branches into array

.github/workflows/plugin_test.yaml

@@ -64,9 +64,11 @@ jobs:
       - name: Check if branch exists
         id: check-branch
         run: |
-          branch_exists=false
-          branches=(${{ matrix.branches }})
-          for branch in ${branches[@]}; do
+          # Split the branches into an array
+          IFS=',' read -ra branches <<< "${{ matrix.branches }}"
+
+          # Check each branch for existence
+          for branch in "${branches[@]}"; do
             echo "Checking branch: $branch"
             if git ls-remote --heads https://github.com/FAIRmat-NFDI/${{ matrix.plugin }}.git $branch | grep -q "refs/heads/$branch"; then
               echo "Branch $branch exists."