Update .gitlab-ci.yml

.gitlab-ci.yml

@@ -3,6 +3,10 @@ stages:
 
 demo:
   stage: build
-  image: alpine
+  image: alpine/git
   script:
     - echo "Running demo CI job for GitHub commit ${GITHUB_COMMIT_ID=(none)}"
+    - git clone https://github.com/${GITHUB_REPO}.git
+    - cd $(basename "${GITHUB_REPO}")
+    - git fetch origin "${GITHUB_COMMIT_ID}"
+    - git checkout "${GITHUB_COMMIT_ID}"