The number of branches for wiredtiger/wiredtiger Github repository grows over time, making the branch dropdown list hard to use. According to history, lots of those stale branches are feature/testing branches that were merged or abandoned (and possibly forgot to be removed). 

Instead of relying on manual reminding, it would be great to have some automatic checking function in place to periodically (e.g. once per month) probe all branches in Github repository to figure out those stale branches, then send an email/slack to branch owners for follow-up (either retaining or deleting the branches).