What is the difference between git diff HEAD vs. git diff --staged?

Question

What is the difference between git diff HEAD and git diff --staged? I tried both but both give the same output.

Answer 1

You can also get different output from the two diff commands if you are running them on an unsuccessful merge, i.e. unmerged paths.

I have not been able to find out why it behaves like this, but you could read more about it here