CI to check for coding style (#15404)

CONTRIBUTING.md

@@ -37,6 +37,8 @@ For your proposed change, you need to have:
 * **an issue** (in the issue tracker) which describe your bug or feature
 * **a feature branch** in your git fork
 
+Make sure your code change follows the style guide. To format your code, run `./tools/format-code.sh`.
+
 ### Refer the Issue
 
 The commit message needs to link to the issue. This cross-reference is [very important](http://ariya.ofilabs.com/2012/01/small-scale-software-craftsmanship.html) for the following reasons.

azure-pipelines.yml

@@ -1,5 +1,16 @@
 jobs:
 
+- job: 'CodeQuality'
+  pool:
+    vmImage: 'macOS 10.13'
+  steps:
+  - script: brew install clang-format && clang-format --version
+    displayName: 'Install clang-format'
+  - script: bash ./tools/format-code.sh
+    displayName: 'Run code formatter'
+  - script: git diff --quiet HEAD
+    displayName: 'Check if the styling guide is followed'
+
 - job: 'amd64_linux_gcc'
   pool:
     vmImage: 'ubuntu-18.04'

tools/format-code.sh

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+
+cwd=$(pwd)
+clang-format -i --style=WebKit $cwd/src/*.h $cwd/src/*.cpp