The following the commands to do that.
$git checkout ( E.g master )
$git fetch upstream
$git pull upstream ( E.g master )
$git checkout ( E.g branch where is your PR )
$git rebase ( E.g master )
$git push origin + // force push
Solutions for developers
The following the commands to do that.
$git checkout ( E.g master )
$git fetch upstream
$git pull upstream ( E.g master )
$git checkout ( E.g branch where is your PR )
$git rebase ( E.g master )
$git push origin + // force push