CI: Add workflow to build mkdocs in GHA (#5152)

Build core and addons, then create mkdocs site as an artifact. Addons addons, but ignores errors with addons.

Gets addons according to the version (breaks for major version transitions when addons branch may not exist), rebuild keywords, rename file.

ARCH needs to be defined (any value should do). Skeleton code to makes addon build logs available.

Gets the logs before the docs, fails if no docs.

Author: wenzeslaus

.github/workflows/documentation.yml

@@ -0,0 +1,150 @@
+---
+name: Documentation
+
+# Builds Markdown documentation for core and addons.
+
+on:
+  push:
+    branches:
+      - main
+      - releasebranch_*
+  pull_request:
+  workflow_dispatch:
+
+permissions: {}
+
+jobs:
+  ubuntu:
+    concurrency:
+      group: ${{ github.workflow }}-${{ github.event_name == 'pull_request' && github.head_ref || github.sha }}
+      cancel-in-progress: true
+
+    runs-on: ubuntu-22.04
+    env:
+      PYTHONWARNINGS: always
+      # renovate: datasource=python-version depName=python
+      PYTHON_VERSION: "3.12"
+
+    steps:
+      - name: Checkout core
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+        with:
+          repository: OSGeo/grass
+          path: grass
+
+      - name: Get dependencies
+        run: |
+          sudo apt-get update -y
+          sudo apt-get install -y wget git gawk findutils
+          xargs -a <(awk '! /^ *(#|$)/' "grass/.github/workflows/apt.txt") -r -- \
+              sudo apt-get install -y --no-install-recommends --no-install-suggests
+
+      - name: Set up Python
+        uses: actions/setup-python@42375524e23c412d93fb67b49958b491fce71c38 # v5.4.0
+        with:
+          python-version: ${{ env.PYTHON_VERSION }}
+          cache: pip
+
+      - name: Create installation directory
+        run: |
+          mkdir "$HOME/install"
+
+      - name: Set number of cores for compilation
+        run: |
+          echo "MAKEFLAGS=-j$(nproc)" >> "$GITHUB_ENV"
+
+      - name: Set LD_LIBRARY_PATH for compilation
+        run: |
+          echo "LD_LIBRARY_PATH=$HOME/install/lib" >> "$GITHUB_ENV"
+
+      - name: Build core
+        run: |
+          cd grass
+          ../grass/.github/workflows/build_ubuntu-22.04.sh "$HOME/install"
+
+      - name: Add the bin directory to PATH
+        run: |
+          echo "$HOME/install/bin" >> "$GITHUB_PATH"
+
+      - name: Print installed versions
+        if: always()
+        run: ./grass/.github/workflows/print_versions.sh
+
+      - name: Test executing of the grass command
+        run: ./grass/.github/workflows/test_simple.sh
+
+      - name: Set version variables
+        run: |
+          cd grass
+          eval $(./utils/update_version.py status --bash)
+          echo "MAJOR=$MAJOR" >> $GITHUB_ENV
+          echo "MINOR=$MINOR" >> $GITHUB_ENV
+          echo "VERSION=$VERSION" >> $GITHUB_ENV
+          echo "YEAR=$YEAR" >> $GITHUB_ENV
+
+      - name: Checkout addons
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+        with:
+          repository: OSGeo/grass-addons
+          ref: grass${{ env.MAJOR }}
+          path: grass-addons
+
+      - name: Compile addons
+        continue-on-error: true
+        run: |
+          ./grass-addons/utils/cronjobs_osgeo_lxd/compile_addons_git.sh \
+            "$MAJOR" \
+            "$MINOR" \
+            $(pwd)/grass-addons/src \
+            $(grass --config path) \
+            $(pwd)/addons-build-dir \
+            grass
+
+      - name: Get target path for Markdown files
+        run: |
+          echo MKDOCS_DIR="$(grass --config path)/docs/mkdocs" >> "$GITHUB_ENV"
+
+      - name: Move from build to target directory
+        continue-on-error: true
+        run: |
+          mkdir -p "$MKDOCS_DIR/source/addons"
+          mv addons-build-dir/docs/md/source/* "$MKDOCS_DIR/source/addons"
+
+      - name: Rebuild keywords
+        continue-on-error: true
+        run: |
+          export ARCH="linux"
+          export ARCH_DISTDIR="$(grass --config path)"
+          export TOP_DOCS_DIR="${ARCH_DISTDIR}/docs"
+          export VERSION_NUMBER="$VERSION"
+          grass --tmp-project XY --exec python grass/man/build_keywords.py "$TOP_DOCS_DIR" "$MKDOCS_DIR/source/addons"
+
+      - name: Get mkdocs
+        run: |
+          pip install -r "grass/man/mkdocs/requirements.txt"
+
+      - name: Run mkdocs
+        run: |
+          cd grass
+          eval $(./utils/update_version.py status --bash)
+          cd ..
+          export SITE_NAME="GRASS GIS $VERSION Reference Manual"
+          export COPYRIGHT="&copy; 2003-$YEAR GRASS Development Team, GRASS GIS $VERSION Reference Manual"
+          cd $MKDOCS_DIR
+          mkdocs build
+
+      - name: Make logs available
+        uses: actions/upload-artifact@65c4c4a1ddee5b72f698fdd19549f0f0fb45cf08 # v4.6.0
+        with:
+          name: grass-addon-build-logs
+          if-no-files-found: warn
+          path: addons-build-dir/docs/logs
+          retention-days: 3
+
+      - name: Make the result available
+        uses: actions/upload-artifact@65c4c4a1ddee5b72f698fdd19549f0f0fb45cf08 # v4.6.0
+        with:
+          name: mkdocs-site
+          if-no-files-found: error
+          path: ${{ env.MKDOCS_DIR }}/site
+          retention-days: 3