Skip the test gate on docs-only branches

.gitea/workflows/ci.yml

@@ -8,7 +8,28 @@ jobs:
     runs-on: docker-host
     steps:
       - uses: actions/checkout@v4.2.2
-      - run: bash ci.sh
+        with:
+          fetch-depth: 0 # the merge-base below needs history; checkout defaults to depth 1
+      - name: Detect a docs-only branch
+        id: scope
+        run: |
+          git fetch --no-tags --quiet origin +refs/heads/main:refs/remotes/origin/main
+          base=$(git merge-base refs/remotes/origin/main HEAD) \
+            || { echo 'No merge-base with main - running the gate'; echo 'docs_only=false' >> "$GITHUB_OUTPUT"; exit 0; }
+          changed=$(git diff --name-only "$base" HEAD)
+          printf '%s\n' "$changed"
+          # Skip only when there IS a diff and every path is *.md. An empty diff, an unreadable
+          # range, anything else - fall through to the gate.
+          if [ -n "$changed" ] && ! printf '%s\n' "$changed" | grep -qvE '\.md$'; then
+            echo 'docs_only=true' >> "$GITHUB_OUTPUT"
+          else
+            echo 'docs_only=false' >> "$GITHUB_OUTPUT"
+          fi
+      - name: Full gate
+        if: steps.scope.outputs.docs_only != 'true'
+        run: bash ci.sh
+      # Never gated on docs_only: release.yml re-tags this exact image, and ff-only merges make
+      # every branch head a main commit - a main commit without an image is an unreleasable one.
       - name: Push app image tagged with the commit hash
         env:
           IMAGE: gitea.larvit.se/${{ github.repository }}:${{ github.sha }}