For a complete current list of Github keyboard shortcuts, visit:
From that page:
Nearly every page on GitHub has a keyboard shortcut to perform actions faster. Typing ? in GitHub brings up a dialog box that lists the keyboard shortcuts available for that page. You can use these keyboard shortcuts to perform actions across the site without using your mouse to navigate.
A few of the most useful:
You can use find, and search/replace!
|Find||control f||command f|
|Find Next||control g||command g|
|Find Previous||shift control f||shift command f|
|Replace||shift control f||command option f|
|Replace All||shift control r||command shift option f|
You can also go directly to a specific line/column, and use undo/redo:
|Goto Line/Column||alt g||option g|
|Undo||control z||command z|
|Redo||control y||command y|