Show branch name on mouse over graph

I notice with my coworkers when they are working with SourceTree (for the first time) that it's sometime difficult for them to understand what the branch is that belongs to a line in the graph column.

Therefore I think it would be a great help if a mouse over on the graph would show a small message telling what the corresponding branch name is. I created a small example of what this might look like, see the attachment "Example mouse over.png"