only commit if there is a change to at least one of the license files

Author: elrayle

.github/workflows/fetch-licenses.yaml

@@ -27,6 +27,10 @@ jobs:
                   cp spdx-license-list-data/json/licenses.json cmd/licenses.json
                   cp spdx-license-list-data/json/exceptions.json cmd/exceptions.json
 
+            - name: Check for changes
+              run: |
+                  git diff --exit-code -- cmd/licenses.json cmd/exceptions.json || exit 0
+                
             - name: Commit and push
               run: |
                   git config --local user.email "[email protected]"