Triangular workflow

I wonder if we can come up with a flexible and
extensible notation to specify what branch(es) to compare with, so
that we can use it as the value of this opt-in configuration
variable?  Something like

        [status] compareBranches = @{upstream} @{push}

If we go with that, then it becomes trickier code-wise to show push/pull
advice for the correct branches. But not impossible since we can check if
branch is the same as @{upstream} or @{push}.

Philosophically, two main git commands are 'git push' and 'git pull'. So it
makes perfect sense to me to signal that those two are special, and not
allow other compareBranches.


Harald