code: function changelog(from, to) {
      return vowExec(util.format('git log --format="%%s" %s..%s', from, to))
          .then(function (stdout) {
              return stdout.split('\n');
          });
  }
docs: Extracts changes from git history.
  
  @param {String} from Reference to a point in the history, starting from which
  changes will be extracted. Starting point will be the very first commit
  if an empty string's provided.
  @param {String} to Reference to a point in the history, up to which changes
  will be extracted. If an empty string's provided change'll include all
  commits after the starting point.
  @param {vow.Promise} Promise that'll be fulfilled with an array of commits'
  subject strings.