The Refined GitHub add-on is amazing, if you are a GitHub user.

The GitHub addon that I must have.
Love this addon. My life is better with this addon.

Thank you.

Adds very useful quality of life improvements to Github

Extremely useful. Especially when selecting a diff only selects the code and ignores the + and - symbols

Worth getting if only because it lets you copy and paste directly from diffs!

(But many other lovely touches: basically indispensable)

Very useful!

Very Good

Firefox Quantum is fast and looks great. But this add-on is what really helped pull me away from Safari.