Stacker is a Chrome add-on developed by riku.rouvila that aims to simplify the management of stacked pull requests on Github. This free tool enhances Github's user interface and provides additional features to streamline the pull request workflow.

With Stacker, users can mark a pull request as dependent on their previous work, allowing for better organization and tracking of dependencies. This feature is particularly useful when dealing with complex projects with multiple interconnected pull requests.

Another key feature of Stacker is the ability to only view the changes made in the pull request you are reviewing. This eliminates the need to sift through unrelated changes, saving time and improving focus.

Additionally, Stacker provides automatic warnings for pull request dependencies. This ensures that users are aware of any potential conflicts or issues that may arise due to dependencies between pull requests.

Overall, Stacker is a valuable add-on for Github users who frequently work with stacked pull requests. It enhances the user experience by simplifying the management of dependencies and providing a more streamlined workflow.