Option to allow packages from backports but without forcing it

[Pirate Praveen <praveen@onenetbeyond.org>]

Hi,

I have been using "apt -t buster-backports install gitlab" till 
recently. But with ruby 2.7 in buster-fasttrack, I need to tell apt to 
prefer packages in buster-fasttrack when it has a newer version than 
fasttrack.

For example, ruby-nokogiri is available in buster-backports (built with 
ruby 2.5) and buster-fasttrack (built with ruby 2.7). So current 
options I have is,

1. apt install <list packages present in both backports and fasttrack> 
&& apt -t buster-backports install gitlab
1. aptitude -t buster-backports install gitlab and press n and second 
option picks all required packages from fasttrack

Can this be done in a single apt command/first aptitude option with 
some magical command line arguments?