add global-json-file input (#276)

* support specifying global.json location with global-json-file input

* add test workflow jobs for global.json usage

* fix typo in global-json-file description

Co-authored-by: Brian Cristante <33549821+brcrista@users.noreply.github.com>

Co-authored-by: Brian Cristante <33549821+brcrista@users.noreply.github.com>

.github/workflows/workflow.yml

@@ -163,6 +163,32 @@ jobs:
         shell: pwsh
         run: __tests__/verify-dotnet.ps1 3.1 2.2
 
+  test-setup-global-json-specified-and-version:
+    runs-on: ${{ matrix.operating-system }}
+    strategy:
+      fail-fast: false
+      matrix:
+        operating-system: [ubuntu-latest, windows-latest, macOS-latest]
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+      - name: Clear toolcache
+        shell: pwsh
+        run: __tests__/clear-toolcache.ps1 ${{ runner.os }}
+      - name: Write global.json
+        shell: bash
+        run: |
+          mkdir subdirectory
+          echo '{"sdk":{"version": "2.2","rollForward": "latestFeature"}}' > ./subdirectory/global.json
+      - name: Setup dotnet
+        uses: ./
+        with:
+          dotnet-version: 3.1
+          global-json-file: ./subdirectory/global.json
+      - name: Verify dotnet
+        shell: pwsh
+        run: __tests__/verify-dotnet.ps1 2.2 3.1
+
   test-proxy:
     runs-on: ubuntu-latest
     container: