What is UnityPackageManager/manifest.json?

The folder UnityPackageManager appeared in the project when I upgraded to Unity 2017. It contains the file manifest.json which contains:

Code (JavaScript):

1. {
2.         "dependencies": {
3.         }
4. }
5.  

This made me curious as it seems to be something related to package management, which Unity has been lacking. But this file seems undocumented. Searching turns up nothing except a post that asks whether it should be under version control (which it should, apparently).

So what is this file for?

 

I have the same question

Found those informations about the subject :

https://forum.unity.com/threads/unitypackagemanager-directory-should-be-included-in-svn.498480/

https://docs.unity3d.com/2017.2/Documentation/Manual/ExternalVersionControlSystemSupport.html

But no clear answer so far ...

 

So, still no information about it?
It is something like nuget ?

 

It seems it can actually be used for package management, even for custom packages: https://gist.github.com/LotteMakesStuff/6e02e0ea303030517a071a1c81eb016e