rerun if mtime changes.

go/qst.go

func runAndWatch(file string, cmd string) {
	// run command, if file changes (mtime) restart command
	// for now: run command until it exits, wait a bit, run again
	runShellCmd(cmd)
	time.Sleep(1 * time.Second)
	runAndWatch(file, cmd)
	lastMtime := time.Unix(0, 0)
	for {
		info, err := os.Stat(file)
		if err != nil {
			log.Fatalf("Error: %s disappeared, exiting.", file)
		}
		mtime := info.ModTime()
		if mtime.After(lastMtime) {
			log.Printf("%s changed, rerunning", file)
			runShellCmd(cmd)
		}
		lastMtime = mtime
		time.Sleep(1 * time.Second)
	}
}
func runShellCmd(cmd string) {