ci: Do not run clang-tidy-diff when also running full clang-tidy

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

@@ -22,6 +22,7 @@ clang-tidy:
   variables:
     MPI_CI: 1
     CLANG_TIDY_OUTPUT: clang-tidy-output.log
+    FILES_CHANGED: git-diff-name-only.log
   before_script:
     - apt update
     - DEBIAN_FRONTEND=noninteractive apt install -y
@@ -43,17 +44,21 @@ clang-tidy:
       git remote add upstream https://gitlab.com/nsnam/ns-3-dev.git ;
       fi
     - git fetch upstream $CI_DEFAULT_BRANCH
+    - git diff --name-only upstream/$CI_DEFAULT_BRANCH > $FILES_CHANGED
 
-    # Run clang-tidy-diff. If running on default branch, Git diff is empty and this is ignored.
+    # Run clang-tidy-diff in the opposite cases of the if-else below.
     # File paths generated by git diff are relative to the working tree. Therefore, iregex should only contain paths relative to the working tree.
-    - git diff -U0 upstream/$CI_DEFAULT_BRANCH |
+    - if !([[ $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH ]] || (grep -q ".clang-tidy" $FILES_CHANGED)) ; then
+      echo "Running clang-tidy-diff" ;
+      git diff -U0 upstream/$CI_DEFAULT_BRANCH |
       clang-tidy-diff-14.py -path cmake-cache/ -p1 -quiet -use-color
       -iregex "(contrib|examples|src|scratch|utils)\/.+\.(cpp|cc|cxx|c|h|hpp)"
       1> $CLANG_TIDY_OUTPUT
-      2> /dev/null
+      2> /dev/null ;
+      fi
 
     # Run full clang-tidy in the following cases: 1) default branch, 2) ".clang-tidy" file changed, 3) clang-tidy-diff had an error
-    - if [[ $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH ]] || (echo $(git diff --name-only upstream/$CI_DEFAULT_BRANCH) | grep -q ".clang-tidy") || (egrep -q -A 3 "file not found \[clang-diagnostic-error\]" $CLANG_TIDY_OUTPUT) ; then
+    - if [[ $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH ]] || (grep -q ".clang-tidy" $FILES_CHANGED) || (egrep -q -A 3 "file not found \[clang-diagnostic-error\]" $CLANG_TIDY_OUTPUT) ; then
       echo "Running full clang-tidy" ;
       run-clang-tidy-14 -p cmake-cache/ -quiet
       1> $CLANG_TIDY_OUTPUT