GitHub is the largest code hosting service in existence, but only now is it getting back into producing mobile apps. The company released an Android app in 2012, then removed it in 2015. Two months ago, GitHub revealed that a brand new app would enter beta soon, and now it has finally arrived.
GitHub said the new mobile apps would only focus on providing functionality that software developers might want on the go. While you can browse through repositories, share feedback in discussions, perform searches, and more, you can't actually view code unless it is part of a merge request. Only the README file in each repository is visible.
The app does seem to work, though I would have appreciated the ability to view code — I've been in situations a few times where I wanted to quickly share code examples with someone, and finding them using the new app would likely be much faster than GitHub's fairly-terrible mobile site. Perhaps that functionality will arrive in a later update.