Publish nuget from action

Author: andersnm

.github/workflows/build.yml

@@ -25,4 +25,42 @@ jobs:
       - uses: actions/upload-artifact@v4
         with:
           name: nupkg
-          path: "**/*.nupkg"
+          path: src/ExcelNumberFormat/bin/Release/*.nupkg
+          if-no-files-found: error
+
+  publish:
+    needs: build
+    if: startsWith(github.ref, 'refs/tags/v')
+    runs-on: ubuntu-latest
+    permissions:
+      id-token: write
+    steps:
+      - uses: actions/download-artifact@v4
+        with:
+          name: nupkg
+          path: nupkg
+
+      - name: Verify tag matches package version
+        run: |
+          shopt -s nullglob
+          files=(nupkg/*.nupkg)
+          if [ ${#files[@]} -ne 1 ]; then
+            echo "Expected exactly one nupkg, found ${#files[@]}"; exit 1
+          fi
+          expected="nupkg/ExcelNumberFormat.${GITHUB_REF_NAME#v}.nupkg"
+          if [ "${files[0]}" != "$expected" ]; then
+            echo "Tag $GITHUB_REF_NAME does not match package ${files[0]} (expected $expected). Update VersionPrefix in the csproj."; exit 1
+          fi
+
+      - uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: 10.0.x
+
+      - name: NuGet login (trusted publishing)
+        id: login
+        uses: NuGet/login@v1
+        with:
+          user: ${{ vars.NUGET_USER }}
+
+      - name: Push
+        run: dotnet nuget push "nupkg/*.nupkg" --source https://api.nuget.org/v3/index.json --api-key ${{ steps.login.outputs.NUGET_API_KEY }} --skip-duplicate