* Show checkout instructions also when there is no permission to push,
for anyone who wants to locally test the changes.
* First checkout the branch exactly as is, without immediately having to
solve merge conflicts. Leave this to the merge step, since it's often
convenient to test a change without worrying about this.
* Use `git fetch -u`, so an existing local branch is updated when
re-testing the same pull request. But not the more risky `git fetch -f`
in to handle force pushes, as we don't want to accidentally overwrite
important local changes.
* Show different merge command depending on the chosen merge style,
interactively updated.
7a286e4753