How might I watch/copy files in Cakefile as I develop?

Currently I have setup a cake task to watch and compile CoffeeScript, Jade, Stylus like: 

task "startdev", "Starts server with nodemon and watch files for changes", ->
    # start nodemon server
    nodemon = spawn procExec("nodemon"), ["server.coffee"]
    processOutput nodemon

    # watch and compile CoffeeScript
    coffee = spawn procExec("coffee"), ["-o", "public/js/app", "-cw", "client/coffee"]
    processOutput coffee

    # watch and compile Stylus
    stylus = spawn procExec("stylus"), ["client/stylus/styles.styl", "-I", "public/css/","-l", "-w", "-u", "./node_modules/nib", "-o", "public/css/app"]
    processOutput stylus

    # watch and compile jade
    jade = spawn procExec("jade"), ["client/jade/index.jade", "--out", "public"]
    processOutput jade

Now, I want to watch for file changes in a folder and copy it to another folder (aka sync folders, copy files from src to public). How might I do that? I think its fine if the solution is not specific to Node/JS, as long as I dont have to download a whole bunch and lots of setup to make it work.

After some research, perhaps I should use a build too like jake? But how do I use it to sync 2 folders

You may use watch to do this:

watch = require 'watch'

task 'watch', 'watches for file and copy/compiles them', ->
  # watch file changes
  watch.watchTree 'src', (f, curr, prev) ->
    return if typeof f is "object" && prev is null && curr is null
    return if f.match(/\.(coffee)$/)
    dest = 'lib' + f[3..]
    if curr.nlink is 0
      fs.unlinkSync dest if fs.existsSync dest
      log "removed " + dest
    else 
      oldFile = fs.createReadStream f
      newFile = fs.createWriteStream dest
      oldFile.pipe newFile
      log "copied " + f + ' to ' + dest
  log 'Watching to copy files', green  
  # watch_coffee
  ...