ports tree in git, python port, setuptools_scm

[Andriy Gapon]

I have a strange problem in, maybe, an unusual setup.
I have a ports tree cloned from git.
I am building a port in a traditional old-fashioned way where the work directory
is under the port's directory.
The port is for python software and it uses setuptools for installation.
When I install the port it takes a very long time and I see that it is because
of this child process:
    git archive --prefix /usr/ports/ HEAD
I tracked it down to site-packages/setuptools_scm/file_finder_git.py.
I guess it is designed to get some version information when building some
software from a git checkout.  But in my case `git rev-parse --show-toplevel`
returns the path to the ports tree and, so, the command works on the whole ports
tree.

Is this a known issue?
Is there an easy workaround?
One thing that comes to mind is setting WRKDIRPREFIX.

Thanks!
-- 
Andriy Gapon