Document and test the cancel() method on the object returned by atom.workspace.scan().

src/workspace.coffee

@@ -803,7 +803,8 @@ class Workspace extends Model
   #   * `onPathsSearched` (optional) {Function}
   # * `iterator` {Function} callback on each file found
   #
-  # Returns a `Promise`.
+  # Returns a *thenable* object with a `cancel()` method that will cancel all
+  # of the underlying searches that were started as part of this scan.
   scan: (regex, options={}, iterator) ->
     if _.isFunction(options)
       iterator = options