ci: Skip cppyy job if no source code is changed

utils/tests/gitlab-ci-cppyy.yml

@@ -2,6 +2,8 @@ cppyy-22.04:
   stage: test
   image: ubuntu:22.04 # python 3.10
   dependencies: []
+  variables:
+    FILES_CHANGED: git-diff-name-only.txt
   before_script:
     - apt update
     - DEBIAN_FRONTEND=noninteractive apt install -y
@@ -11,6 +13,22 @@ cppyy-22.04:
       git wget
     - pip install cppyy==3.1.2 matplotlib numpy
   script:
+    - if (git remote | grep -qw upstream) ; then
+      git remote remove upstream ;
+      fi
+    - git remote add -t $CI_DEFAULT_BRANCH --no-tags -f upstream https://gitlab.com/nsnam/ns-3-dev.git
+    - git diff --name-only upstream/$CI_DEFAULT_BRANCH | tee $FILES_CHANGED
+
+    # Run this job in the following cases: 1) default branch, 2) changes to source code, 3) changes to configurations.
+    # Skip this job in the opposite cases.
+    # File paths generated by git diff are relative to the working tree.
+    - |
+      if [[ $CI_COMMIT_BRANCH != $CI_DEFAULT_BRANCH ]] &&
+         !(grep -qE ".*\.(cc|h)|CMakeLists.txt|bindings/|build-support/|ns3|utils/tests/.*\.(yaml|yml)" $FILES_CHANGED) ; then
+        echo "No source code or configurations changes found in this MR. Skipping this job.";
+        exit 0;
+      fi
+
     - ./ns3 configure -G Ninja --enable-python-bindings
     - ./ns3 build
     - ./ns3 run first.py