This is re-make of old, centered view of Github
Why new styles is bad
The new styles are trying to spread to all available width of the screen on big monitors, enforcing the user to jump back and forth with his eyes, instead of compactly presenting information, as it was before.
I think the authors of new UI tried to use the "scientific research" which presents people's eyes movement heatmap that is mostly distributed on the left side. But you don't need heatmaps to make good UI. Moreover, this research most likely was performed not on software developers who use Github. This does not make any sense I think, to break normal, centered, compact view, and shift it to the left side of the screen just to match it with some irrelevant heatmap. Sometimes you just don't need a bunch of scientific papers to make something that is good and productive.
The button gradient removal is also a poor design decision. A change to make a change? Just to follow Flat Design guidelines? What's Github now, a mobile app?
Another concern about the new styles is that they use round avatars which do not add anything useful, they just reduce the quantity of information that you are seeing on the avatar image. This is the change that is also partially reversed.