fix: append mode

Author: c-dilks

.github/workflows/submodule.yml

@@ -19,9 +19,7 @@ jobs:
         id: changes
         run: |
           for sm in $(grep 'path = ' .gitmodules | awk '{print $3}'); do
-            echo "SUBMODULE $sm ===========" | tee changes.txt
-            git diff origin/${{ github.base_ref }} --submodule=log -- $sm | tee changes.txt
-            echo "" | tee changes.txt
+            git diff origin/${{ github.base_ref }} --submodule=log -- $sm | tee -a changes.txt
           done
           echo "changes<<EOF" >> $GITHUB_OUTPUT
           cat changes.txt >> $GITHUB_OUTPUT