You can zoom into a folder displayed in the browser by double-clicking on the item. The selected folder will become the new root of the browser.
Double clicking on package files such as .nib and .pages files will open the file in the owner app. You can override this behavior to zoom into the folder in the browser by holding down the Option (⌥) key while double-clicking on the folder.
You can open a folder in Finder by holding down Command (⌘) while double-clicking the folder. Command-double clicking a file reveals that file in Finder.
The browser maintains a history which can be navigated using the back and forward buttons in the top-left corner of the browser:
The path bar situated at the top of the browser can be used to navigate up towards the root of the repository from the current folder:
In the above example, std is the current folder. To navigate back to the root folder, click on the boost segment.