GitHub UI Extensions is a free Chrome extension developed by gizumon. This extension enhances the user experience on GitHub by providing additional features. With GitHub UI Extensions, users can easily check the base branch and head branch of a pull request in both the pull request list and detail pages. This helps prevent unintended merging by implementing custom branch name validation rules.

The main features of GitHub UI Extensions include displaying alerts for the base and head branches in the pull request list page and detail page. This allows users to quickly identify the branches involved in each pull request. Additionally, the extension supports regular expression branch validation rules, providing users with more control over the merging process. It's worth noting that all these features are compatible with GitHub Enterprise.

Using GitHub UI Extensions is straightforward - simply install the extension and start benefiting from its features immediately. For users who want to set up branch validation rules, there is an optional feature to configure the "Merge Regular Expression Blacklist" from the extension's option page.