try fetch depth is 0

.github/workflows/matrix-commit-message.yml

@@ -8,7 +8,7 @@ jobs:
       - name: checkout
         uses: actions/checkout@v2
         with:
-          fetch-depth: 20
+          fetch-depth: 0
       - run: |
           ALL_MSGS=""
           for i in ${{ join(github.event.commits.*.id, ' ') }}; do