ci: Add clang-tidy-diff job

utils/tests/gitlab-ci-code-linting.yml

@@ -2,6 +2,7 @@
 #
 # Contains jobs to check the ns-3 coding style and perform lint checking.
 
+# Clang-format
 check-style-clang-format:
   stage: code-linting
   image: ubuntu:latest
@@ -14,38 +15,73 @@ check-style-clang-format:
     - python3 utils/check-style-clang-format.py .
   timeout: 1h
 
-clang-tidy:
+# Clang-tidy
+.base-clang-tidy:
   stage: code-linting
   image: ubuntu:latest
   variables:
     MPI_CI: 1
     CLANG_TIDY_OUTPUT: clang-tidy-output.log
+    GIT_DEPTH: 0
   before_script:
     - apt update
     - DEBIAN_FRONTEND=noninteractive apt install -y
       clang cmake
-      clang-tidy-14
+      clang-tidy clang-tidy-14
       python3 python3-pip
       libboost-all-dev libgtk-3-dev libopenmpi-dev libsqlite3-dev
       gsl-bin libgsl-dev libgsl27
-      ssh
+      git ssh
     - pip3 install cppyy
-  script:
     - ./ns3 configure -d debug
       --enable-clang-tidy
       --enable-examples --enable-tests --enable-asserts
       --enable-mpi --enable-python-bindings
-    - run-clang-tidy-14 -p cmake-cache/ -quiet
-      1> clang-tidy-errors.log
-      2> /dev/null
-    - (! egrep -A 3 "error:|warning:|note:" $CLANG_TIDY_OUTPUT)
-    - echo "No clang-tidy errors found"
   artifacts:
     paths:
       - $CLANG_TIDY_OUTPUT
     when: on_failure
   timeout: 3h
 
+clang-tidy:
+  extends: .base-clang-tidy
+  rules:
+    - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH
+      when: on_success
+    - changes:
+        paths:
+          - .clang-tidy
+        compare_to: master
+      when: on_success
+  script:
+    - run-clang-tidy-14 -p cmake-cache/ -quiet
+      1> $CLANG_TIDY_OUTPUT
+      2> /dev/null
+    - (! egrep -A 3 "error:|warning:|note:" $CLANG_TIDY_OUTPUT)
+    - echo "No clang-tidy errors found"
+
+clang-tidy-diff:
+  extends: .base-clang-tidy
+  rules:
+    - if: $CI_PIPELINE_SOURCE == "merge_request_event"
+      when: never
+    - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH
+      when: never
+    - changes:
+        paths:
+          - .clang-tidy
+        compare_to: master
+      when: never
+    - when: on_success
+  script:
+    - git diff -U0 $(git merge-base --fork-point origin/$CI_DEFAULT_BRANCH) |
+      clang-tidy-diff-14.py -path cmake-cache/ -p1 -quiet
+      1> $CLANG_TIDY_OUTPUT
+      2> /dev/null
+    - (! egrep -A 3 "error:|warning:|note:" $CLANG_TIDY_OUTPUT)
+    - echo "No clang-tidy errors found"
+
+# Emacs line
 emacs-line:
   stage: code-linting
   image: ubuntu:latest