What variables do colcon.pkg and setup.cfg accept?

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Hi,

I am building a python colcon package and would like to understand the variables supported by the files colcon.pkg and setup.cfg.

As per the example in ROS2 docs here , setup.cfg has a variable called $base in it.

I also have an environment hook that I am installing through setup.py and defining it in colcon.pkg.

Is there a variable for the package name, just like $base, that can be used instead of explicitly defining it the above files? Also I would like to know where can I find the reference to all allowed variables for both these files.

Thanks,

Arpit