git.cmd.coffee

git.cmd = (args, options={}) ->
  new Promise (resolve, reject) ->
    output = ''
    try
      new BufferedProcess
        command: atom.config.get('git-plus.gitPath') ? 'git'
        args: args
        options: options
        stdout: (data) -> output += data.toString()
        stderr: (data) -> reject data.toString()
        exit: (code) -> resolve output
    catch
      notifier.addError 'Git Plus is unable to locate the git command. Please ensure process.env.PATH can access git.'
      reject "Couldn't find git"

# New usage      
stagedFiles = (repo) ->
  args = ['diff-index', '--cached', 'HEAD', '--name-status', '-z']
  git.cmd(args, cwd: repo.getWorkingDirectory())
  .then (data) -> # handle data
  .catch (error) -> # handle error