[gentoo-python] How to migrate to the new scheme of Python scripts?

[Michał Górny]

Hello,

Since the idea hasn't seen negative feedback so far, I think we should
so some early thinking on how to migrate.

Good news is that it doesn't change anything at all for packages
installed already. They will still use dev-python/python-exec:0
at least until they're rebuilt, so there's no risk of immediate
breakage during the upgrade.

However, the upgrade itself seems harder to accomplish. Specifically,
all the simple ways of achieving that would involve changing stable
packages.


It should be noted that what changes is:

1. Wrapped scripts are moved to a new location,

2. Wrappers are replaced by another branch of python-exec.

So, this doesn't apply to the packages which don't install
Python scripts at all. For the remaining ones, external behavior
persists -- EPYTHON is respected, /usr/bin/foo works.

The only things that break is those explicitly relying on wrapping
logic, and I track them in a bug:

  https://bugs.gentoo.org/show_bug.cgi?id=484398


So far, I can think of three solutions, starting with the worst:

1. Deploy the new stuff in an overlay (except for python-exec:2 itself),
keep it there for some time asking people to test with eclasses
overriding the main tree. Then ask arch teams to stabilize
python-exec:2. When it hits stable, move the changes to the tree.

2. Make the new features controlled via make.conf variable. Ask users
to test with it enabled, then file a stablereq for arch teams to test
with the switch enabled, plus stabilize the few packages which will
need direct changes. Then remove the switch and make the new behavior
default for all stuff.

3. python-r2, python-single-r2, distutils-r2 :).


Anyone has a better idea?

-- 
Best regards,
Michał Górny