Hi,
I'm not expert at all, but since I suffer from the lack of "real" (safe
without being overkill) upgrading software in pkgsrc, I decided to write
once. Actually It does nothing, it only prints a shellscript to stdout,
containing the list of the commands that should be executed (the list of
the package needing upgrade, in proper order).

Get it: http://fab.gnux.info/progs/pykg_upgrade.py

You can test it without fearing it, since it just prints to stdout.

I found some difficulties:

 - package renaming (so they aren't here anymore)
 - dependencies added (it shouldn't be too hard to implement)
 - outdated dependencies (the code should handle that, but it results in
   a mess, so I commented out the code)

Please, feel free to send patches and comments, I'm being busy for a
week or more but I'll read my mails as well.
It's python, easy to understand and modify even if you don't already
know it. If we get something working very well, I'll try to re-write it
in plain C.

Fabien Devaux.

PS: Don't forget to CC me, I'm not on the list