added buildinfo command

Makefile

@@ -1,7 +1,10 @@
+VERSION=0.1-pre
+VERSION_SUFFIX=
+
 all: install test lint vet
 
 install:
-	go install github.com/kopia/kopia/cmd/kopia
+	go install -ldflags "-X main.buildVersion=$(VERSION) -X main.buildTime=`date -u '+%s'` -X main.buildGitHash=`git describe --dirty`" github.com/kopia/kopia/cmd/kopia
 
 build:
 	go build github.com/kopia/kopia/...
@@ -28,7 +31,7 @@ dev-deps:
 	go get -u github.com/newhook/go-symbols
 	go get -u github.com/sqs/goreturns
 
-test:
+test: install
 	go test -timeout 30s github.com/kopia/kopia/...
 
 vtest:

cmd/kopia/command_buildinfo.go

@@ -0,0 +1,37 @@
+package main
+
+import (
+	"fmt"
+	"strconv"
+	"time"
+
+	"gopkg.in/alecthomas/kingpin.v2"
+)
+
+var (
+	buildInfoCommand = app.Command("buildinfo", "Show build information").Hidden()
+
+	buildVersion = "UNKNOWN"
+	buildGitHash = "UNKNOWN"
+	buildTime    = ""
+)
+
+func buildTimeString() string {
+	t, err := strconv.ParseInt(buildTime, 10, 64)
+	if err == nil {
+		return time.Unix(t, 0).Format(time.RFC3339)
+	}
+
+	return "UNKNOWN"
+}
+
+func init() {
+	buildInfoCommand.Action(runBuildInfoCommand)
+}
+
+func runBuildInfoCommand(context *kingpin.ParseContext) error {
+	fmt.Println("Version:", buildVersion)
+	fmt.Println("Hash:   ", buildGitHash)
+	fmt.Println("Built:  ", buildTimeString())
+	return nil
+}

cmd/kopia/main.go

@@ -17,11 +17,13 @@
 )
 
 var (
-	app = kingpin.New("kopia", "Kopia - Online Backup").Version("0.0.1").Author("http://kopia.github.io/")
+	app = kingpin.New("kopia", "Kopia - Online Backup").Author("http://kopia.github.io/")
 )
 
 func main() {
 	log.SetFlags(0)
+	log.SetOutput(os.Stderr)
+	app.Version(buildVersion)
 	kingpin.MustParse(app.Parse(os.Args[1:]))
 	return
 }