ci(openclaw): skip image build when no openclaw-related files changed

Add openclaw-changes gate job that uses git diff to detect changes in openclaw-relevant paths (packages/openclaw-image/, packages/default.nix, flake.nix, flake.lock, ci.yml). The build-and-push-openclaw job now only runs when the gate reports changed=true, avoiding unnecessary Docker image builds on unrelated pushes to main.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

.gitea/workflows/ci.yml

@@ -108,11 +108,59 @@ jobs:
         env:
           NIX_CONFIG: "access-tokens = git.johnogle.info=${{ secrets.GITEA_ACCESS_TOKEN }}"
 
-  build-and-push-openclaw:
-    name: Build & Push OpenClaw Image
+  openclaw-changes:
+    name: Check OpenClaw Changes
     runs-on: ubuntu-latest
     needs: check
     if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+    outputs:
+      changed: ${{ steps.filter.outputs.changed }}
+    steps:
+      - uses: actions/checkout@v6
+        with:
+          fetch-depth: 0
+
+      - name: Check for OpenClaw-related changes
+        id: filter
+        run: |
+          # Files/directories that affect the openclaw image build
+          OPENCLAW_PATHS=(
+            'packages/openclaw-image/'
+            'packages/default.nix'
+            'flake.nix'
+            'flake.lock'
+            '.gitea/workflows/ci.yml'
+          )
+
+          PREV_SHA="${{ github.event.before }}"
+          # If before sha is all zeros (new branch), compare against initial commit
+          if [ "$PREV_SHA" = "0000000000000000000000000000000000000000" ]; then
+            PREV_SHA=$(git rev-list --max-parents=0 HEAD)
+          fi
+
+          # If the before SHA doesn't exist in the repo (e.g. force push),
+          # fall back to comparing against the previous commit on the branch
+          if ! git rev-parse "$PREV_SHA" >/dev/null 2>&1; then
+            echo "Warning: before SHA $PREV_SHA not found, falling back to HEAD^"
+            PREV_SHA="HEAD^"
+          fi
+
+          CHANGED=false
+          for path in "${OPENCLAW_PATHS[@]}"; do
+            if git diff --name-only "$PREV_SHA" "${{ github.sha }}" -- "$path" | grep -q .; then
+              echo "Change detected in: $path"
+              CHANGED=true
+              break
+            fi
+          done
+
+          echo "changed=$CHANGED" >> $GITHUB_OUTPUT
+
+  build-and-push-openclaw:
+    name: Build & Push OpenClaw Image
+    runs-on: ubuntu-latest
+    needs: openclaw-changes
+    if: needs.openclaw-changes.outputs.changed == 'true'
     outputs:
       image_tag: ${{ steps.meta.outputs.tag }}
     steps: