Configure default push remote branch
The first time you pull changes from a repository, or clone via Magit, a prompt in the mini-buffer asks if the current remote branch should be used as the default remote repository to push to.
P p will push changes to the default push remote repository. A list of remotes is shown if no default remote is set.
Changing the default remote
The default push remote can be selected from remote repositories added as a remote, by cloning or using the
M remote menu in the Magit Status buffer.
P to open the push menu
C to open the configuration of the local repository
P to toggle the default upstream branch between remotes
u to add a new upstream branch as the default, showing a list of all possible remote branches.
RTN to choose a branch
G-g to close the configuration menu. Then either
u to pull from the new default upstream branch, or
C-g to exit the pull menu.