How to fetch and extract patches in archives?

[Zero King]

Hi,

Port w3m needs patches from Debian to fix security issues. Currently,
the patches are added to the ports tree and takes ~800KiB. Since its
size will grow, I'd prefer to fetch the patches from Debian archives
(e.g. w3m_0.5.3-36.debian.tar.xz).

I tried to add the archive and ${workpath}/.../020_debian.patch to
distfiles and patchfiles, but that didn't work because port(1) attempted
to fetch the patchfiles into ${distpath} and `DEBUG: Fetching distfile
failed: No such file or directory`.

-- 
Best regards,
Zero King
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