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.github/workflows/build-docs.yml

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+name: Build OpenAPI docs
+on: 
+  - push
+  # - pull_request
+jobs:
+  docs-build:
+    runs-on: ubuntu-latest
+    # env:
+    #   TRAVIS_BRANCH: ${{ github.event.number }} 
+    #   a trick that builds docs for PRs (with PR number). Does not work for PRs from forks.
+    steps:
+      - name: Setup Node.js environment
+        uses: actions/setup-node@v2.5.1
+        with: 
+          node-version: 14.x
+          # Comes with npm 6. For newer Node, encountered: https://github.com/npm/cli/issues/3359
+      - run: npm install -g @redocly/openapi-cli && npm install -g redoc-cli
+      - run: npm install -g gh-openapi-docs
+      - name: Check out repository code
+        uses: actions/checkout@v2
+      - run: gh-openapi-docs
+      - name: Deploy 🚀
+        uses: JamesIves/github-pages-deploy-action@v4.2.2
+        with:
+          branch: gh-pages
+          folder: .