Add script to check for missing license headers

Also adds a `check_license` target to the Makefile to run the script

Makefile

@@ -25,6 +25,10 @@ style:
 	@echo ">> checking code style"
 	@! gofmt -d $(shell find . -path ./vendor -prune -o -name '*.go' -print) | grep '^'
 
+check_license:
+	@echo ">> checking license header"
+	@./scripts/check_license.sh
+
 test:
 	@echo ">> running tests"
 	@$(GO) test -short $(pkgs)
@@ -54,5 +58,5 @@ assets:
 	@go-bindata $(bindata_flags) -pkg ui -o web/ui/bindata.go -ignore '(.*\.map|bootstrap\.js|bootstrap-theme\.css|bootstrap\.css)'  web/ui/templates/... web/ui/static/...
 
 
-.PHONY: all style format build test vet docker assets tarballs
+.PHONY: all style check_license format build test vet docker assets tarballs
 

scripts/check_license.sh

@@ -0,0 +1,10 @@
+#!/bin/sh
+
+licRes=$(
+for file in $(find . -type f -iname '*.go' ! -path './vendor/*'); do
+	head -n3 "${file}" | grep -Eq "(Copyright|generated|GENERATED)" || echo -e "  ${file}"
+done;)
+if [ -n "${licRes}" ]; then
+	echo -e "license header checking failed:\n${licRes}"
+	exit 255
+fi