CI to catch missing `make format`

.travis.yml

@@ -5,6 +5,16 @@ cache: ccache
 matrix:
   fast_finish: true
   include:
+  - os: linux
+    dist: xenial
+    compiler: gcc
+    env: MAKE_TARGET=format-verify PATH="/usr/lib/llvm-8/bin:$PATH"
+    addons:
+      apt:
+        sources:
+          - llvm-toolchain-xenial-8
+        packages:
+          - clang-format-8
   - os: linux
     dist: xenial
     compiler: gcc
@@ -77,6 +87,7 @@ addons:
     packages:
     - binutils-gold
     - build-essential
+    - clang-format
     - cmake
     - curl
     - docker-ce

Makefile

@@ -243,6 +243,9 @@ abyss: debug
 format:
 	clang-format -i $$(find jni daemon llarp include libabyss | grep -E '\.[h,c](pp)?$$')
 
+format-verify: format
+	git diff --quiet || echo 'Please run make format!!' && git --no-pager diff && false
+
 analyze-config: clean
 	mkdir -p '$(BUILD_ROOT)'
 	$(ANALYZE_CONFIG_CMD)