Best way to get submodules into extracted source?

[Zhenfu Shi]

Hey guys,
I’m trying updating transmission(-x11) to just-released version 3.0, but it uses a lot of 3rd party submodules. I found the macports guide reads "the best distfile candidate (if available) is a distfile from GitHub releases”, so I’d like to know what’s the best way to put submodules into the extracted tarball, without using `fetch.type git` and `git submodule update —init`. Would be great if there’s a port already doing this so I could learn from it.

Thanks in advance!