how to maintain multiple active versions of a port (e.g. octave)?

[Ray Zimmerman]

I am the developer of a Matlab/Octave package that I need to test against multiple versions of Matlab and Octave. I’ve been using MacPorts to build and install Octave on my system and was wondering what is the best way to …

 (1) keep older versions of a port when the port is updated to use a new version of the sources. E.g. the octave port was using octave 3.8.0 sources and has recently changed to 4.0.3. How can I keep the 3.8.0 version available (I can create differently named symlinks to point to the binaries), while allowing MacPorts to build and install the new octave 4.0.3?

(2) build a previous version of a port, again without eliminating the current version. E.g. I recently upgraded to OS X Sierra and had to rebuild all of my ports, so now I have octave 4.0.3, but I’d like to go back and re-install 3.8.0, which I need for testing (without eliminating 4.0.3).

Thanks in advance,

    Ray