Update fmt target

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <[email protected]>

Makefile

@@ -2,13 +2,18 @@ Version := $(shell git describe --tags --dirty)
 GitCommit := $(shell git rev-parse HEAD)
 LDFLAGS := "-s -w -X github.com/alexellis/arkade/cmd.Version=$(Version) -X github.com/alexellis/arkade/cmd.GitCommit=$(GitCommit)"
 PLATFORM := $(shell ./hack/platform-tag.sh)
+SOURCE_DIRS = cmd pkg main.go
 
 .PHONY: all
 
 .PHONY: build
 build:
 	go build
 
+.PHONY: fmtcheck
+fmt: ## Checks for style violation using gofmt
+	@gofmt -l -s $(SOURCE_DIRS) | grep ".*\.go"; if [ "$$?" = "0" ]; then echo "Run gofmt -w -s ./path" && exit 1; fi
+
 .PHONY: test
 test:
 	CGO_ENABLED=0 go test $(shell go list ./... | grep -v /vendor/|xargs echo) -cover