Compile Emacs from CVS as a port?

[Kai Grossjohann]

I use Emacs from CVS on a daily basis.  Currently, I have a working
copy which build and install into a subdir of my home directory.

But I think building Emacs as a port might provide advantages in
integrating with add-on packages that are available as ports, such as
AUCTeX.

I searched a bit, but everything I could find assumed that the source
code for the program to build is available as a tarball, whereas I
have a CVS working copy.

Does anyone have pointers?  Perhaps somebody has done what I need
already?

tia,
Kai