Maintaining source code for selected ports.

[Ben Tompkins]

I apologize if this question has already been answered, but I am new to this board and could not find a way to search
the archives. So far I have been running an "easy" binary installation of macports without changing any of the defaults,
which results in the source code getting deleted following each successful install. Now I would like to download the source code for selected ports, which may or may not have been installed through macports as binaries on my system, for offline browsing. I see that there is a system wide option (portautoclean [default=yes]), apparently to prevent macports from cleaning any source/intermediate files for all future installs, but this strikes me as somewhat heavy-handed, and I don't like the idea of habitually modifying a system-wide configuration file according as I do or do not want to keep the source code for a given port. Of course, if that is indeed the best and/or only way to preserve the source code for selected ports, then I will do it, but I suspect strongly that there is a better way and seek guidance regarding this issue.