How should multiple (related) projects be arranged (structured) and configured so that they can share code, have a related package structure and enable proper unittesting, and ensuring no namespace collisions

[Paddy]

Thanks alisonken1, I did indeed mean that when you have production code
and test code then its time to bring in the version control systems.
But having said that ;-) i have been naughty in the past and used the
-s or --symbolic-link option of the gnu cp (sometimes available as
gcp), command which copies a whole directory tree of the production
release to a test area, copying directories but putting links in to the
original files. I make sure that the production code is all read-only
thenwork in the test area. If I need to modify a file I:
 * list the link
 * remove the link, replacing it with a copy of the file linked to
 * get write priviliges to the new copy
 * edit the copy.

But we should all be using a version control system right :-)

- paddy.