One _big_ script block (since it seems like FS edits are not persistent across steps?)

Author: weswigham

.github/workflows/new-release-branch.yaml

@@ -9,30 +9,23 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
+    - name: Use node version 12.x
+      uses: actions/setup-node@v1
+      with:
+        node-version: 12.x
     - uses: actions/checkout@v2
       with:
         fetch-depth: 5
-    - uses: actions/checkout@v2
     - run: |
         git checkout -b ${{ github.event.client_payload.branch_name }}
-    - name: update package.json version and corePublic.ts version
-      run: |
         sed -i -e 's/"version": ".*"/"version": "${{ github.event.client_payload.package_version }}"/g' package.json
         sed -i -e 's/const versionMajorMinor = ".*"/const versionMajorMinor = "${{ github.event.client_payload.core_major_minor }}"/g' src/compiler/corePublic.ts
         sed -i -e 's/const versionMajorMinor = ".*"/const versionMajorMinor = "${{ github.event.client_payload.core_major_minor }}"/g' tests/baselines/reference/api/typescript.d.ts
         sed -i -e 's/const versionMajorMinor = ".*"/const versionMajorMinor = "${{ github.event.client_payload.core_major_minor }}"/g' tests/baselines/reference/api/tsserverlibrary.d.ts
         sed -i -e 's/const version = `${versionMajorMinor}.0-.*`/const version = `${versionMajorMinor}.0-${{ github.event.client_payload.core_tag || 'dev' }}`/g' src/compiler/corePublic.ts
-    - name: Use node version 12.x
-      uses: actions/setup-node@v1
-      with:
-        node-version: 12.x
-    - name: gulp LKG
-      run: |
         npm install
         gulp LKG
         npm test
-    - uses: actions/checkout@v2
-    - run: |
         git diff
         git add package.json
         git add src/compiler/corePublic.ts