Check formatting only on files modified wrt master

.gitlab-ci.yml

@@ -83,7 +83,10 @@ coding-conventions:
   script:
     - export LCG_release_area=${LCG_release_area}:/cvmfs/lhcb.cern.ch/lib/lcg/external
     - sudo pip install autopep8==1.3.5
-    - make BUILDDIR=${BUILDDIR} apply-formatting
+    - make BUILDDIR=${BUILDDIR} configure
+    - git fetch https://gitlab.cern.ch/gaudi/Gaudi.git master
+    - git diff --name-only --no-renames --diff-filter MA FETCH_HEAD..HEAD | grep -E '\.(h|i?cpp|py)$' |
+      xargs --no-run-if-empty ${BUILDDIR}/apply-formatting || true
     - "echo \"From: Gitlab CI <noreply@cern.ch>\" > apply-formatting.patch"
     - "echo \"Date: $(date -R)\" >> apply-formatting.patch"
     - "echo \"Subject: [PATCH] Fixed formatting\" >> apply-formatting.patch"