To use the keyboard you must first focus the graph by clicking in it.
To move around the graph you can either use the mouse or the keyboard.
Click and drag.
Scroll all the way left (first commit).
Scroll all the way right (last commit).
Scroll all the way up vertically.
Scroll all the way down vertically.
mouse over a commit dot
Show the author, commit id, and commit message for that commit.
click a commit dot
Go to that specific commit in the owner's repository.
t Toggle the visibility of the head labels