enforcing branch names for labs

prebuild_lab_0:

  stage: lab0

  script:

    - echo "Changes Detected (if any):";

    - git diff --name-only $CI_COMMIT_SHA~ $CI_COMMIT_SHA || echo "No changes found";

    - echo "$CI_COMMIT_REF_NAME"

    - |

      # Check if lab0.cpp exists

      if [ ! -f "lab0.cpp" ]; then