Understanding Git workflow around DEP-14

[deb251@lewenberg.com]

I am packaging some upstream software for Debian and I am trying to 
understand the workflow around "DEP-14: Recommended layout for Git 
packaging repositories".

Looking at DEP-14 I might have these Git branches:

  master
  debian/master
  debian/stretch
  upstream/latest

I understand that the Debian packaging files in debian/ will appear in 
the "debian/*" branch, but my general question is: what is the workflow 
around all these branches? When and how do files get merged from one 
branch to another?


More specifically:

1. Besides the debian/ directory, what is the difference between the 
"debian/master" branch and the "upstream/latest" branch?

2. What should the "master" branch be used for?

3. When a new upstream tarball is released, where should it be imported? 
In "upstream/latest"? In "debian/master"? Both?


Thanks, Adam Lewenberg