use $GITHUB_HEAD_REF to get branch name when sharing preivew

.github/workflows/share-preview-url.yml

@@ -19,17 +19,11 @@ jobs:
       - name: install sst
         run: |
           curl -fsSL https://ion.sst.dev/install | VERSION=0.1.51 bash
-      - name: set branch name
-        id: get_branch_name
-        run: |
-          BRANCH_NAME=${{ github.event.pull_request.head.ref }}
-          SANITIZED_BRANCH_NAME=$(echo "$BRANCH_NAME" | sed 's/[^a-zA-Z0-9]/-/g')
-          echo "SS_STAGE=$SANITIZED_BRANCH_NAME" >> $GITHUB_OUTPUT
       - name: retrieve sst app url
         id: get_app_url
         working-directory: ./previews
         run: |
-          echo "PREVIEW_APP_URL=$(sst shell node get_app_url.js --stage=${{ steps.set_branch_name.outputs.BRANCH_NAME }})" >> "GITHUB_OUTPUT"
+          echo "PREVIEW_APP_URL=$(sst shell node get_app_url.js --stage=$GITHUB_HEAD_REF)" >> "GITHUB_OUTPUT"
       - name: get dest dir for web smart-camera-web
         id: get_dest_dir_smart_camera_web
         working-directory: ./packages/smart-camera-web