A user said, "We have multiple branch histories and, more importantly, several subtrees (incl. an upstream Pressflow Drupal distro, several modules, etc) which each have a long commit history. It's difficult to see where things connect with more than a few history lines on the screen, esp. if there is a long list of commits (e.g. in ancestor order).
What I am thinking would be useful is the ability to "toggle" visibility of these history lines by branch, or perhaps even by an unnamed subtree merge.

I would like to toggle visibility of subsets of branches, not just view a single branch in isolation with the existing functionality"