Add a workflow for building the docs

.github/workflows/docs.yml

@@ -0,0 +1,81 @@
+name: publish-doc
+
+on:
+  push:
+    branches:
+       - 'master'
+       - 'docs-on-gh-pages'
+    tags:
+      - v*-*
+  workflow_dispatch:
+
+concurrency:
+  group: pages
+  cancel-in-progress: true
+
+jobs:
+  build-doc:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v4
+    - uses: actions/configure-pages@v4
+    - uses: cvmfs-contrib/github-action-cvmfs@v3
+    - uses: aidasoft/run-lcg-view@v4
+      with:
+        container: el9
+        view-path: /cvmfs/sw-nightlies.hsf.org/key4hep
+        run: |
+          echo "::group::Install dependencies"
+          python3 -m pip install -r doc/requirements.txt
+          export PATH=/root/.local/bin:$PATH
+
+          echo -e "::endgroup::\n::group::Build podio"
+          cmake -B build . --install-prefix=$(pwd)/install \
+                -GNinja -DENABLE_SIO=ON -DENABLE_RNTUPLE=ON \
+                -DBUILD_TESTING=OFF \
+                -DCMAKE_CXX_STANDARD=17
+          cmake --build build --target install
+          export PYTHONPATH=$(pwd)/install/python:$PYTHONPATH
+          export LD_LIBRARY_PATH=$(pwd)/install/lib*/:$LD_LIBRARY_PATH
+          export ROOT_INCLUDE_PATH=$(pwd)/install/include
+
+          echo -e "::endgroup::\n::group::build doc"
+          sphinx-build -M html doc doc_output
+
+    - name: Upload artifact
+      uses: actions/upload-pages-artifact@v3
+      with:
+        path: doc_output/html
+
+  publish-doc:
+    needs: build-doc
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          ref: gh-pages
+      - uses: actions/download-artifact@v4
+        with:
+          name: github-pages
+          path: doc_artifact
+
+      - name: Update documentation
+        env:
+          TARGET_DIR: ${{ github.ref_name }}
+        run: |
+          mkdir -p ${TARGET_DIR}
+          rm -rf ${TARGET_DIR}/*
+          tar -xvf doc_artifact/artifact.tar --directory ${TARGET_DIR}
+          rm -r doc_artifact
+
+      - name: Commit and push changes
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          TARGET_DIR: ${{ github.ref_name }}
+        run: |
+          git config --global user.email ${GITHUB_ACTOR_ID}+${GITHUB_ACTOR}@users.noreply.github.com
+          git config --global user.name ${GITHUB_ACTOR}
+          git add ${TARGET_DIR}
+          git diff-index --quiet HEAD 2>&1 > /dev/null || git commit -m "Update documentation for ${TARGET_DIR}" && git push

doc/requirements.txt

@@ -2,3 +2,5 @@ breathe
 myst-parser
 sphinx
 sphinx_rtd_theme
+sphinx_copybutton
+sphinx_multiversion