Github Manager Extension is a free Chrome add-on developed by dev.davkal. This extension provides software maintenance metrics on the issues pages of Github repositories. It focuses on bug metrics and displays them in an easily accessible manner.

One of the key features of this extension is the use of BMI (backlog management index). The BMI is calculated based on the number of closed issues divided by the number of opened issues during a specific period, multiplied by 100. A BMI larger than 100 indicates that the backlog of bugs was reduced during that period.

It's worth noting that only issues labeled as "bug" are counted in the metrics provided by this extension. This ensures that the displayed metrics accurately reflect the bug management performance.

Overall, Github Manager Extension is a valuable tool for developers and Github users who want to track and analyze bug metrics on Github repositories. With its open-source code available on Github, users can also contribute to its development and improvement.