add cmd 'bee update' to update self

just notice once a day if there is a new version

cmd/commands/update/update.go

@@ -0,0 +1,38 @@
+package update
+
+import (
+	"flag"
+	"os"
+	"os/exec"
+
+	"github.com/beego/bee/cmd/commands"
+	"github.com/beego/bee/config"
+	beeLogger "github.com/beego/bee/logger"
+)
+
+var CmdUpdate = &commands.Command{
+	UsageLine: "update",
+	Short:     "Update Bee",
+	Long: `
+Automatic run command "go get -u github.com/beego/bee" for selfupdate
+`,
+	Run: updateBee,
+}
+
+func init() {
+	fs := flag.NewFlagSet("update", flag.ContinueOnError)
+	CmdUpdate.Flag = *fs
+	commands.AvailableCommands = append(commands.AvailableCommands, CmdUpdate)
+}
+
+func updateBee(cmd *commands.Command, args []string) int {
+	beeLogger.Log.Info("Updating")
+	beePath := config.GitRemotePath
+	cmdUp := exec.Command("go", "get", "-u", beePath)
+	cmdUp.Stdout = os.Stdout
+	cmdUp.Stderr = os.Stderr
+	if err := cmdUp.Run(); err != nil {
+		beeLogger.Log.Warnf("Run cmd err:%s",err)
+	}
+	return 0
+}