Merge pull request #6 from itsdalmo/add_version_flag

Suggestion for version flag in binary.

Makefile

@@ -3,17 +3,19 @@ TARGET ?= darwin
 ARCH ?= amd64
 EXT ?= ""
 DOCKER_REPO=itsdalmo/ssm-sh
+TRAVIS_TAG ?= ref-$(shell git rev-parse --short HEAD)
+LDFLAGS=-ldflags "-X=main.version=$(TRAVIS_TAG)"
 SRC=$(shell find . -type f -name '*.go' -not -path "./vendor/*")
 
 default: test
 
 run: test
 	@echo "== Run =="
-	go run main.go
+	go run $(LDFLAGS) main.go
 
 build: test
 	@echo "== Build =="
-	go build -o $(BINARY_NAME) -v
+	go build -o $(BINARY_NAME) -v $(LDFLAGS)
 
 test:
 	@echo "== Test =="
@@ -40,6 +42,6 @@ build-docker:
 
 build-release:
 	@echo "== Release build =="
-	CGO_ENABLED=0 GOOS=$(TARGET) GOARCH=$(ARCH) go build -o $(BINARY_NAME)-$(TARGET)-$(ARCH)$(EXT) -v
+	CGO_ENABLED=0 GOOS=$(TARGET) GOARCH=$(ARCH) go build $(LDFLAGS) -o $(BINARY_NAME)-$(TARGET)-$(ARCH)$(EXT) -v
 
 .PHONY: default build test build-docker run-docker build-release

command/root.go

@@ -3,6 +3,7 @@ package command
 var Command RootCommand
 
 type RootCommand struct {
+	Version func()       `short:"v" long:"version" description:"Print the version and exit."`
 	List    ListCommand  `command:"list" alias:"ls" description:"List managed instances."`
 	Shell   ShellCommand `command:"shell" alias:"sh" description:"Start an interactive shell."`
 	Run     RunCommand   `command:"run" description:"Run a command on the targeted instances."`

command/version.go

@@ -0,0 +1,16 @@
+package command
+
+import (
+	"fmt"
+	"os"
+)
+
+// CommandVersion (overridden in main.go)
+var CommandVersion = "unknown"
+
+func init() {
+	Command.Version = func() {
+		fmt.Println(CommandVersion)
+		os.Exit(0)
+	}
+}

main.go

@@ -6,7 +6,11 @@ import (
 	"os"
 )
 
+// Version is set on build by the Git release tag.
+var version string
+
 func main() {
+	command.CommandVersion = version
 	_, err := flags.Parse(&command.Command)
 	if err != nil {
 		if flagsErr, ok := err.(*flags.Error); ok && flagsErr.Type == flags.ErrHelp {