Update build comment if it already exists

This changes the workflow to update the existing comment about the test build if that comment already exists. It embeds a hidden field within the comment body to find it.

Since some PRs get force pushed a lot, particularly Renovate ones, this prevents a very long line of repeated comments.

Author: nmburgan

.github/workflows/main.yml

@@ -163,14 +163,23 @@ jobs:
           path: output/
           retention-days: 1 # quite low retention, because the artifacts are quite large
           overwrite: true # overwrite old artifacts if a PR runs again (artifacts are per PR * per project)
-      - name: Add comment
+      - name: Find existing comment
+        uses: peter-evans/find-comment@v3
+        if: github.event.pull_request.head.repo.full_name == github.repository
+        id: find-comment
+        with:
+          issue-number: ${{ github.event.pull_request.number }}
+          comment-author: 'github-actions[bot]'
+          body-includes: '<!-- build-artifacts -->'
+      - name: Add or update comment
         uses: peter-evans/create-or-update-comment@v5
-        # Check if the event is not triggered by a fork
-        # https://github.com/peter-evans/create-pull-request/blob/main/docs/concepts-guidelines.md#restrictions-on-repository-forks
         if: github.event.pull_request.head.repo.full_name == github.repository
         with:
+          comment-id: ${{ steps.find-comment.outputs.comment-id }}
           issue-number: ${{ github.event.pull_request.number }}
+          edit-mode: replace
           body: |-
+            <!-- build-artifacts -->
             The rpm/deb packages and the JAR file for openvoxdb are available in a zip archive:
             ${{ steps.upload.outputs.artifact-url }}