Multiple Python versions from version-file in one environment

This makes the change from #567 also available for users of
.python-version.

.github/workflows/test-python.yml

@@ -271,3 +271,29 @@ jobs:
           }
           $pythonVersion
         shell: pwsh
+
+  setup-python-multiple-python-versions-from-file:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+    steps:
+      - uses: actions/checkout@v3
+      - name: Build multi-version file
+        run: printf '%s\n' 3.7 3.8 3.9 3.10 > .python-version
+        shell: bash
+      - name: Setup Python and check latest
+        uses: ./
+        with:
+          python-version-file: '.python-version'
+          check-latest: true
+      - name: Validate version
+        run: |
+          $pythonVersion = (python --version)
+          if ("$pythonVersion" -NotMatch "3.10"){
+            Write-Host "The current version is $pythonVersion; expected version is 3.10"
+            exit 1
+          }
+          $pythonVersion
+        shell: pwsh