Add travis job with clang-format

Author: awegrzyn

.travis.yml

@@ -0,0 +1,26 @@
+language: cpp
+matrix:
+  include:
+    - os: linux
+      dist: xenial
+      env: TOOL=clang-format
+      addons:
+        apt:
+          sources:
+            - llvm-toolchain-xenial-7
+          packages:
+            - clang-format-7
+      compiler: clang
+script:
+  - if [[ $TOOL == "clang-format" ]] && [ "$TRAVIS_PULL_REQUEST" != "false" ]; then
+      cd $TRAVIS_BUILD_DIR;
+      BASE_COMMIT=$(git rev-parse $TRAVIS_BRANCH);
+      COMMIT_FILES=$(git diff --name-only $BASE_COMMIT | grep -i -v LinkDef);
+      RESULT_OUTPUT="$(git-clang-format-7 --commit $BASE_COMMIT --diff --binary `which clang-format-7` $COMMIT_FILES)";
+      if [ "$RESULT_OUTPUT" == "no modified files to format" ] || [ "$RESULT_OUTPUT" == "clang-format did not modify any files" ] ; then
+        exit 0;
+      else
+        echo "$RESULT_OUTPUT";
+        exit 1;
+      fi
+    fi