Seconded. This is one of the pain-points I wish github would address. The constantly broken "network graph" and complete lack of (meaningful) tools to compare forks or branches is a royal pain in the ass.

Many of the missing operations ("In which branches does commit X exist", "Show delta between A,B") shouldn't even be hard to implement.

I don't understand why github spends their resources on useless gimmicks ("streaks", "pop repos") rather than pushing their core product.