Viewing and comparing branches
The Branches page allows you to monitor the activity across branches. To view it, click Branches at the top of the revisions list:
You can quickly search and compare the branches and see which ones are active or stale.
The Set default branch button (available to project administrators) will take you to the project configuration screen where this setting can be specified. When the default branch is set, the UI becomes a bit smarter when displaying the commits graph, rendering README files, comparing branches, etc.