What is the function of --poll flag in CLI

In cases where Angular CLI is running in a shared directory on linux VM on a windows host the webpack dev server isn't detecting file changes from the host environment. (ex: Whenever a docker dev environment is running on a windows host.) This is solved by adding poll option to the webpack dev server configuration. By default when no poll interval is set watchpack will use native file system change detection. This change allows for setting the poll interval which will turn on polling.

Ref: Comment by JSMike on feat(webpackDevServer): Add watchOptions for webpackDevServer in angular / angular-cli | GitHub

The correct usage is --poll ms and not --poll = ms.
For example:

ng serve --poll 2000