What does the argument @{u} mean in Git?
Solution 1:
It is a shortcut to refer to the upstream branch which the current branch is tracking. So for instance if you're on branch topic/fix_blub which is tracking origin/topic/fix_blub then git merge @{u} does the same thing as git merge origin/topic/fix_blub.
@{u} is part of Git's mini-language for locating revisions, which is described in detail here.