Replace git command by only-changes gitlab ci rules.

The goal is to execute C++ test only when a change occurred in core or tests.

.gitlab-ci.yml

@@ -39,8 +39,9 @@ stages:
 ctest:
     variables: {SLOW_TESTS: "OFF", BUILD_MULTITHREAD: "ON"} # the CDashConfScript is able to retrieve OpenMP_gomp_LIBRARY and OpenMP_INC_DIR from environment (it's necessary on macOS, so the runner's env. must be configured)
     script:
-      # C++ tests are executed only if something was modified in C++ lib or C++ tests
-        - if git log --oneline -n 1 --name-status | grep -E '\s+(src/|misc/test/src/C++)'; then ctest -O ctest.log -S ./CDashConfScript.cmake -j4 --output-junit junit_output.xml; misc/continuous_integration/jobs/junit_html_report.sh cpp_test_report; else echo 'nothing new to test in C++ code'; if grep -B 1 'Outcome:.*Failed' $(ls build*/cpp_test_report.html | tail -1) | sed -ne 's%.*Test case:.*<b>\(.*\)</b>.*%\1%p'; then exit 1; else echo "all tests passed"; exit 0;fi; fi
+        - ctest -O ctest.log -S ./CDashConfScript.cmake -j4 --output-junit junit_output.xml
+        - misc/continuous_integration/jobs/junit_html_report.sh cpp_test_report
+        - if grep -B 1 'Outcome:.*Failed' $(ls build*/cpp_test_report.html | tail -1) | sed -ne 's%.*Test case:.*<b>\(.*\)</b>.*%\1%p'; then exit 1; else echo "all tests passed"; exit 0; fi
     except:
         - schedules
         - tags
@@ -52,6 +53,11 @@ ctest:
             - $(ls -d build*  | tail -1)/cpp_test_report.html
         when:  always
         expire_in: '6 months'
+    only:
+      # C++ tests are executed only if something was modified in C++ lib or C++ tests
+      changes:
+        - src/**
+        - misc/test/src/C++/**
 
 ctest_python:
     before_script: