Gate against go formatting

The `make test` target includes go formatting, if there is any unformatted
code this will lead to a git diff, which the gates now check for.

Change-Id: I52cffadb37c1d42081b56efcae2d977cc0f96f35
Signed-off-by: Sean Eagan <seaneagan1@gmail.com>

Makefile

@@ -114,3 +114,7 @@ $(LINTER): $(TOOLBINDIR)
 
 $(TOOLBINDIR):
 	mkdir -p $(TOOLBINDIR)
+
+.PHONY: check-git-diff
+check-git-diff:
+	@./tools/git_diff_check

playbooks/test-vino.yaml

@@ -59,6 +59,10 @@
       make:
         chdir: "{{ zuul.project.src_dir }}"
         target: test
+    - name: Check git diff
+      make:
+        chdir: "{{ zuul.project.src_dir }}"
+        target: check-git-diff
     - name: Build Docker image
       make:
         chdir: "{{ zuul.project.src_dir }}"

tools/git_diff_check

@@ -0,0 +1,26 @@
+#!/bin/bash
+
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+# Update git index
+git update-index -q --ignore-submodules --refresh
+
+# Evaluate git files for difference, if found print message and fail.
+git diff --exit-code --ignore-submodules
+if [ $? -ne 0 ]
+then
+    echo "error: git diff found, please run make test"
+    exit 1
+fi
+
+echo "success: git diff not found"