grunt-contrib-watchで監視対象のファイルの中で変更されたファイルを取得するサンプル。 Sample to get the files that have been changed in the file to be monitored in the grunt-contrib-watch.

Gruntfile.coffee

module.exports = (grunt) ->

  changedFiles = Object.create null

  # Project configuration.
  grunt.initConfig
    # Metadata.
    pkg: grunt.file.readJSON 'package.json'
    watch:
      coffee:
        files: ['javascripts/**/*.coffee']
        tasks: ['coffeelint']

    coffeelint:
      gruntfile: ['Gruntfile.coffee']
      lib_test: ['javascripts/**/*.coffee']

 # bind watch event
  grunt.event.on 'watch', (status, filepath, taskTargetName) ->
    changedFiles[filepath] = status
    changedCoffeeFile() if /\.(coffee)$/.test filepath

  changedCoffeeFile = ->
    paths = Object.keys changedFiles
    for path in paths
      # Log which file has changed.
      grunt.log.ok "change file is #{path}"
    # Reset changedFiles
    changedFiles = Object.create null
    
  # These plugins provide necessary tasks.
  grunt.loadNpmTasks 'grunt-contrib-watch'
  
  # Default task.
  grunt.registerTask 'default', ['watch']