What config does `git branch --set-upstream-to=origin/ master` actually update?

Question

When you run:

git branch --set-upstream-to=origin/<branch> master

what config does it actually update under .git?

Answer 1

It updates the .git/config file of your current repo, setting remote and merge properties under the specified branch:

[branch "master"]
    remote = origin
    merge = <branch>