[Gnu-arch-users] Sharing individual files/subdirs between projects

[Mikhael Goikhman]

This is a pretty general question that is relevant to umbrella projects.
I think I have an idea about the best solution, but I would like to hear
suggestions from more experienced arch users.

Here are the requirements, reduced for simplicity. Three real projects
are arch-perllib, axp and archzoom.

arch-perllib tree looks like:

    README
    perllib/Arch/         # dozens of files/subdirs
    tests/
    ...

axp tree looks like:

    README
    README.arch-perllib   # shared with arch-perllib README (optional)
    bin/axp
    perllib/Arch/         # shared with arch-perllib
    perllib/AXP/
    tests/

archzoom tree looks like:

    README
    bin/archzoom.cgi
    bin/axp               # shared with axp
    perllib/Arch/         # shared with arch-perllib
    perllib/ArchZoom/
    perllib/AXP/          # shared with axp     
    tests/

There is no requirement for the marked share points to be modifiable.

I see 8 roads toward these requirements.

1) Fork each project from another and delete/add files, then use merging.
This seems to be too problematic to even try, since there are more
unshared files/subdirs than shared ones.

2) Create new smaller projects, one per share point. Not an option.

3) Nest projects (using configs). However this seems to be pretty
problematic with these requirements.

4) Don't nest, but require these projects to be checked out in the same
directory level (possibly using the forth project and configs), then use
out-of-project symlinks to define share points. Works on unix.

5) Keep only one united super-project in arch, with distinct file names.
This is what I do now.

6) Just "cp -a" from one project to another from time to time.

7) Hack a system smarter than "cp -a", to duplicate the structure of
matched changesets (with constraints) from the master project to the
secondary project, and possibly vice versa too. Still no arch involved
in this system (no merging) that makes it difficult for me and others.

8) Wait for the implementation of the Tom's selection idea. Seems like
this is the ultimate solution ... in the future. If I understand it
correctly of course.

So I am basically left with options (4), (5), (6). Do I miss anything?
How would you solve something like this?

Regards,
Mikhael.