Optimize CI/CD builds by skipping when no new commits exist

Add change detection to continuous-integration.yml workflow to prevent
unnecessary builds when no commits have been made since the last
successful build. This reduces resource usage while maintaining the
regular build schedule.

Key changes:
- Check last successful build timestamp via GitHub API
- Compare with latest commit timestamp
- Skip all build steps if no new commits found
- Add clear feedback when builds are skipped
- Maintain existing concurrency controls

Signed-off-by: [email protected]

Author: markpollack

.github/workflows/continuous-integration.yml

@@ -29,6 +29,9 @@ jobs:
     name: Build branch
     runs-on: ubuntu-latest
     if: ${{ github.repository_owner == 'spring-projects' }}
+    permissions:
+      contents: read
+      actions: read
     concurrency:
       group: continuous-integration-${{ github.ref }}
       cancel-in-progress: true  # Skip if another build is running - next cron will trigger soon
@@ -43,20 +46,63 @@ jobs:
       - name: Checkout source code
         uses: actions/checkout@v4
 
+      - name: Check for new commits since last build
+        id: changes
+        run: |
+          # Get the timestamp of the latest commit on this branch
+          LATEST_COMMIT_TIME=$(git log -1 --format="%ct" HEAD)
+          echo "Latest commit timestamp: $LATEST_COMMIT_TIME ($(date -d @$LATEST_COMMIT_TIME))"
+          
+          # Get the last successful build time using GitHub API
+          # Look for the most recent successful CI build on this branch
+          LAST_SUCCESS=$(curl -s \
+            -H "Authorization: Bearer ${{ secrets.GITHUB_TOKEN }}" \
+            -H "Accept: application/vnd.github.v3+json" \
+            "https://api.github.com/repos/${{ github.repository }}/actions/runs?branch=${{ github.ref_name }}&status=success&per_page=50" \
+            | jq -r '.workflow_runs[] | select(.name == "CI/CD build" and .conclusion == "success") | .created_at' \
+            | head -1)
+          
+          if [ -n "$LAST_SUCCESS" ] && [ "$LAST_SUCCESS" != "null" ]; then
+            LAST_SUCCESS_TIME=$(date -d "$LAST_SUCCESS" +%s)
+            echo "Last successful build: $LAST_SUCCESS_TIME ($(date -d @$LAST_SUCCESS_TIME))"
+            
+            if [ "$LATEST_COMMIT_TIME" -le "$LAST_SUCCESS_TIME" ]; then
+              echo "No new commits since last successful build - skipping"
+              echo "skip_build=true" >> $GITHUB_OUTPUT
+              exit 0
+            else
+              echo "New commits found since last successful build - proceeding"
+              echo "skip_build=false" >> $GITHUB_OUTPUT
+            fi
+          else
+            echo "No previous successful build found - proceeding with build"
+            echo "skip_build=false" >> $GITHUB_OUTPUT
+          fi
+
+      - name: Build skipped - no new commits
+        if: steps.changes.outputs.skip_build == 'true'
+        run: |
+          echo "✅ CI/CD build skipped - no new commits since last successful build"
+          echo "This saves resources and reduces unnecessary builds"
+          echo "The next scheduled build will check again for new commits"
+
       - name: Free Disk Space
+        if: steps.changes.outputs.skip_build != 'true'
         uses: jlumbroso/free-disk-space@54081f138730dfa15788a46383842cd2f914a1be # v1.3.1
         with:
           large-packages: false
           docker-images: false
 
       - name: Set up JDK 17
+        if: steps.changes.outputs.skip_build != 'true'
         uses: actions/setup-java@v4
         with:
           java-version: '17'
           distribution: 'temurin'
           cache: 'maven'
 
       - name: Configure Testcontainers
+        if: steps.changes.outputs.skip_build != 'true'
         run: |
           echo "testcontainers.reuse.enable=true" > $HOME/.testcontainers.properties
 
@@ -66,6 +112,7 @@ jobs:
       #     key: docker-${{ runner.os }}-${{ hashFiles('**/OllamaImage.java') }}
 
       - name: Build and test with Maven
+        if: steps.changes.outputs.skip_build != 'true'
         env:
           OPENAI_API_KEY: ${{ secrets.OPENAI_API_KEY }}
           SPRING_AI_OPENAI_API_KEY: ${{ secrets.OPENAI_API_KEY }}
@@ -85,20 +132,20 @@ jobs:
           fi
 
       - name: Generate Java docs
-        if: github.ref == 'refs/heads/main'
+        if: github.ref == 'refs/heads/main' && steps.changes.outputs.skip_build != 'true'
         run: ./mvnw --batch-mode javadoc:aggregate
 
       - name: Generate assembly
-        if: github.ref == 'refs/heads/main'
+        if: github.ref == 'refs/heads/main' && steps.changes.outputs.skip_build != 'true'
         working-directory: spring-ai-docs
         run: ../mvnw --batch-mode assembly:single
 
       - name: Capture project version
-        if: github.ref == 'refs/heads/main'
+        if: github.ref == 'refs/heads/main' && steps.changes.outputs.skip_build != 'true'
         run: echo PROJECT_VERSION=$(mvn help:evaluate -Dexpression=project.version --quiet -DforceStdout) >> $GITHUB_ENV
 
       - name: Setup SSH key
-        if: github.ref == 'refs/heads/main'
+        if: github.ref == 'refs/heads/main' && steps.changes.outputs.skip_build != 'true'
         env:
           DOCS_SSH_KEY: ${{ secrets.DOCS_SSH_KEY }}
           DOCS_SSH_HOST_KEY: ${{ secrets.DOCS_SSH_HOST_KEY }}
@@ -109,7 +156,7 @@ jobs:
           echo "$DOCS_SSH_HOST_KEY" > "$HOME/.ssh/known_hosts"
 
       - name: Deploy docs
-        if: github.ref == 'refs/heads/main'
+        if: github.ref == 'refs/heads/main' && steps.changes.outputs.skip_build != 'true'
         env:
           DOCS_HOST: ${{ secrets.DOCS_HOST }}
           DOCS_PATH: ${{ secrets.DOCS_PATH }}