How to best run a script post installation _and_ deinstallation?

[Gerald Pfeifer]

On Sun, 22 May 2011, Doug Barton wrote:
> Will @unexec in pkg-plist do the job?

On Mon, 23 May 2011, Wesley Shields wrote:
> Are these what you are looking for:
> 
> http://www.freebsd.org/doc/en/books/porters-handbook/pkg-install.html
> http://www.freebsd.org/doc/en/books/porters-handbook/pkg-deinstall.html

Yes and no (to both questions).

I have been looking for a silver bullet that avoids having
  (a) something in the post-install target plus an @exec and an @unexec
      and thus redundancy, or
  (b) two extra scripts and thus two extra files in the port.  

Alas, I failed at that, and Emanuel convinced me that apparently there
is no way to avoid one of these two deaths.

That looks like a nice project for someone to improve our general
infrastructure along these lines.

Gerald