The easiest way to do that is to rename the local branch after pushing.
This shows various levels of brokenness for the reset and rebase to upstream
commands: both menu entries display the wrong upstream branch name in the menu
(the local one rather than the remote one); executing the rebase command works
correctly though, the rebase command uses the right branch name. Resetting
fails, though.
We'll fix this in the next commit.
It is unexpected that a function called PushBranch also sets the upstream
branch; also, we want to add a PushBranch function in the next commit that
doesn't.
