Makefile: version number compiled in for --help

Makefile

@@ -1,13 +1,22 @@
-package = github.com/cultureamp/cfparams
+PACKAGE = github.com/cultureamp/cfparams
+VERSION = $(shell git describe --tags --candidates=1 --dirty)
+FLAGS=-X main.Version=$(VERSION) -s -w
+
+cfparams: main.go
+	go build -ldflags="$(FLAGS)"
+
+.PHONY: install
+install:
+	go install -ldflags="$(FLAGS)" $(PACKAGE)
 
 .PHONY: release
-release: cfparams-darwin-amd64.gz cfparams-linux-amd64.gz
+release: cfparams-$(VERSION)-darwin-amd64.gz cfparams-$(VERSION)-linux-amd64.gz
 
 %.gz: %
 	gzip $<
 
 %-darwin-amd64:
-	GOOS=darwin GOARCH=amd64 go build -o $@ $(package)
+	GOOS=darwin GOARCH=amd64 go build -ldflags="$(FLAGS)" -o $@ $(PACKAGE)
 
 %-linux-amd64:
-	GOOS=linux GOARCH=amd64 go build -o $@ $(package)
+	GOOS=linux GOARCH=amd64 go build -ldflags="$(FLAGS)" -o $@ $(PACKAGE)

main.go

@@ -11,6 +11,9 @@ import (
 	yaml "gopkg.in/yaml.v2"
 )
 
+// see Makefile
+var Version = "dev"
+
 type Input struct {
 	TemplateBody   []byte
 	AcceptDefaults bool
@@ -46,7 +49,8 @@ func main() {
 	var tplFile, paramFile string
 
 	flag.Usage = func() {
-		fmt.Fprintf(os.Stderr, "\nUsage: %s [flags] [Key=value ...]\n\n", os.Args[0])
+		fmt.Fprintf(os.Stderr, "cfparams %s\n\n", Version)
+		fmt.Fprintf(os.Stderr, "Usage: %s [flags] [Key=value ...]\n\n", os.Args[0])
 		fmt.Fprintf(os.Stderr, "Produces JSON suitable for `aws cloudformation` CLI.\n\n")
 		flag.PrintDefaults()
 	}