buildbot: add .travis.yml

Also change .clang-format to support older versions of the tool.

.clang-format

@@ -7,9 +7,9 @@ DerivePointerAlignment: false
 PointerAlignment: Left
 AlignTrailingComments: true
 AllowShortBlocksOnASingleLine: false
-AllowShortCaseLabelsOnASingleLine: false
 AllowShortFunctionsOnASingleLine: false
 AllowShortIfStatementsOnASingleLine: false
 AllowShortLoopsOnASingleLine: false
 ColumnLimit: 0
+AlignTrailingComments: false
 

.travis.yml

@@ -0,0 +1,29 @@
+language: go
+dist: trusty
+
+go:
+  - 1.8.1
+
+before_install:
+  - echo $PATH
+  - export PATH=`echo $PATH | sed -e 's/:\/usr\/local\/clang-3.5.0\/bin//'`
+  - wget http://security.ubuntu.com/ubuntu/pool/main/g/gcc-5/libstdc++6_5.4.0-6ubuntu1~16.04.4_amd64.deb
+  - mkdir ./libc
+  - dpkg-deb -x ./libstdc++6_5.4.0-6ubuntu1~16.04.4_amd64.deb ./libc
+  - export LD_LIBRARY_PATH=`pwd`/libc/usr/lib/x86_64-linux-gnu/
+  - wget http://releases.llvm.org/4.0.1/clang+llvm-4.0.1-x86_64-linux-gnu-debian8.tar.xz
+  - tar -xf ./clang+llvm-4.0.1-x86_64-linux-gnu-debian8.tar.xz
+  - sudo cp clang+llvm-4.0.1-x86_64-linux-gnu-debian8/bin/clang-format /usr/local/bin/
+  - which clang-format
+  - clang-format --version
+
+install: true
+
+script:
+  - make presubmit
+  - test -z $(git diff --name-only) # check that the diff is empty after formatting the code
+
+# If the build fails because some code in not formatted, it's nice to see the diffs after formatting.
+after_failure:
+  - git diff --name-only
+  - git diff