What does the >>= operator do

I was reading the implementation of sort in go, and there is this particular loop in the implementation of func Sort(data Interface):

for i := n; i > 0; i >>= 1 {
    maxDepth++
}

Sort implementation : https://golang.org/src/sort/sort.go

Can someone explain to me what does the >>= operator do ?

Edit: It's simply a shift followed by an affectation. I think the fact it was in a loop bugged my mind.

The >> operator is the right shift operator.

>>= is a contracted form of the right shift operator and assignment:

i >>= 1

It is the same as:

tmp := i >> 1
i = tmp

And that is the same thing as (without the need to create a new variable):

i := i >> 1

Check:
https://golang.org/ref/spec

left shift             integer << unsigned integer

right shift            integer >> unsigned integer

> The shift operators shift the left operand by the shift count
> specified by the right operand. They implement arithmetic shifts if
> the left operand is a signed integer and logical shifts if it is an
> unsigned integer. There is no upper limit on the shift count. Shifts
> behave as if the left operand is shifted n times by 1 for a shift
> count of n. As a result, x << 1 is the same as x*2 and x >> 1 is the
> same as x/2 but truncated towards negative infinity.

Similar questions:

https://stackoverflow.com/questions/5801008/go-and-operators

https://stackoverflow.com/questions/26294372/double-less-operator-in-go-tour-37?lq=1