Add version sub-command (#1389)

Resolves #1369

Makefile

@@ -2,7 +2,7 @@ ORG     ?= $(shell basename $(realpath ..))
 PKGS    := $(shell go list ./... | grep -v /vendor/)
 
 build:
-	go build ${TARGETS}
+	go build -ldflags '-X github.com/roboll/helmfile/pkg/app/version.Version=${TAG}' ${TARGETS}
 .PHONY: build
 
 generate:

main.go

@@ -486,6 +486,15 @@ func main() {
 				return run.ListReleases(c)
 			}),
 		},
+		{
+			Name:      "version",
+			Usage:     "Show the version for Helmfile.",
+			ArgsUsage: "[command]",
+			Action: func(c *cli.Context) error {
+				cli.ShowVersion(c)
+				return nil
+			},
+		},
 	}
 
 	err := cliApp.Run(os.Args)