Deploy docs to Github pages

Author: Matthew-Whitlock

.github/scripts/build-gh-pages.sh

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+#!/bin/bash
+
+set -e
+apt-get update >/dev/null
+apt-get install -y git cmake doxygen graphviz >/dev/null
+
+#List of branches to build docs for
+#TODO: Remove doxygen branch once tested
+BRANCHES="doxygen master develop"
+
+build-docs() (
+    git checkout $1
+
+    #The CMake Doxygen stuff is weird, and doesn't 
+    #properly clean up and/or overwrite old outputs.
+    #So to make sure we get the correct doc configs,
+    #we need to delete everything
+    #We put the docs themselves into a hidden directory
+    #so they don't get included in this glob
+    rm -rf ./*
+
+    cmake ../ -DBUILD_DOCS=ON -DDOCS_ONLY=ON \
+        -DFENIX_DOCS_MAN=OFF -DFENIX_BRANCH=$1 \
+        -DFENIX_DOCS_OUTPUT=$PWD/.docs
+    make doc
+)
+
+git clone https://www.github.com/sandialabs/Fenix.git
+mkdir Fenix/build
+cd Fenix/build
+
+for branch in $BRANCHES; do
+    echo "Building docs for $branch"
+    
+    #TODO: Fail if any branch fails to build,
+    #  once the develop and master branches have doxygen
+    #  merged in
+    build-docs $branch || true
+
+    echo
+    echo
+done
+
+if [ -n "$GITHUB_ENV" ]; then
+    echo "DOCS_DIR=$PWD/.docs" >> $GITHUB_ENV
+fi

.github/workflows/docs.yml

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+name: Publish GH Pages
+
+on:
+  push:
+    branches:
+      - master
+      - develop
+      - doxygen # TODO: Remove after testing
+
+#Only one of this workflow runs at a time
+concurrency:
+  group: docs
+  cancel-in-progress: true
+
+jobs:
+  build-pages:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      
+      - name: Build pages
+        run: /bin/bash .github/scripts/build-gh-pages.sh
+
+      - name: Upload documentation artifact
+        uses: actions/upload-pages-artifact@v3
+        with:
+          path: ${{ env.DOCS_DIR }}
+
+  deploy-docs:
+    needs: build-pages
+    runs-on: ubuntu-latest
+    permissions:
+      pages: write
+      id-token: write
+
+    steps:
+      - name: Deploy documentation to GH Pages
+        uses: actions/deploy-pages@v4
+