ci: doc: post preview comment after build finishes

.github/workflows/docbuild.yml

@@ -34,6 +34,8 @@ jobs:
     steps:
       - name: Checkout sources
         uses: nrfconnect/action-checkout-west-update@main
+        with:
+          git-fetch-depth: 0
 
       - name: cache-pip
         uses: actions/cache@v4
@@ -178,6 +180,32 @@ jobs:
           zip -rq "$ARCHIVE" .
           mv "$ARCHIVE" "$ROOT"
           popd
+
+      - name: Find nRF Connect SDK Edited Documents
+        working-directory: ncs/nrf
+        run: |
+          COMMENT="comment.txt"
+          PREFIX="https://ncsdoc.z6.web.core.windows.net/PR-${{ github.event.pull_request.number }}/"
+          CHANGED=$(git diff --name-only --diff-filter=d "${{ github.event.pull_request.base.sha }}..HEAD")
+
+          echo "You can find the documentation preview for this PR [here](${PREFIX})." >> $COMMENT
+
+          NRF=$(echo "$CHANGED" | \
+                grep -e "doc/nrf/" | \
+                grep -e ".rst" | \
+                sed -e "s#^doc/nrf\(.*\)\.rst#${PREFIX}nrf\1.html#g")
+
+          NRF_EXT=$(echo "$CHANGED" | \
+                    grep -e "applications/" -e "samples/" -e "scripts/" -e "tests/" | \
+                    grep -e ".rst" | \
+                    sed -e "s#^\(applications\|samples\|scripts\|tests\)\(.*\)\.rst#${PREFIX}nrf\/\1\2.html#g")
+
+          NRF_ALL=$(printf "$NRF\n$NRF_EXT")
+
+          if [ ! -z "$NRF_ALL" ]; then
+            printf "\nPreview links for modified nRF Connect SDK documents:\n\n$NRF_ALL" >> $COMMENT
+          fi
+
       - name: Store
         if: ${{ !contains(github.event.pull_request.labels.*.name, 'external') || contains(github.event.pull_request.labels.*.name, 'CI-trusted-author') }}
         uses: actions/upload-artifact@v4
@@ -187,3 +215,4 @@ jobs:
             ncs/nrf/*.zip
             ncs/nrf/monitor*.txt
             ncs/nrf/pr.txt
+            ncs/nrf/comment.txt

.github/workflows/docpublish.yml

@@ -24,6 +24,11 @@ jobs:
           echo "OUTDIR=$OUTDIR" >> "$GITHUB_ENV"
           unzip legacy-ncs*.zip -d $OUTDIR
 
+      - name: Obtain PR number
+        working-directory: docs
+        run: |
+          echo "PR=$(cat pr.txt)" >> "$GITHUB_ENV"
+
       - name: Upload to Azure storage
         working-directory: docs
         env:
@@ -68,3 +73,19 @@ jobs:
             quit
           EOF
           done
+
+      - name: Find Comment
+        uses: peter-evans/find-comment@v3
+        id: fc
+        with:
+          issue-number: ${{ env.PR }}
+          comment-author: 'github-actions[bot]'
+          body-includes: documentation preview
+
+      - name: Create or update comment
+        uses: peter-evans/create-or-update-comment@v4
+        with:
+          comment-id: ${{ steps.fc.outputs.comment-id }}
+          issue-number: ${{ env.PR }}
+          body-path: docs/comment.txt
+          edit-mode: replace