[gentoo-python] Replacing python-wrapper with python-exec

["Michał Górny" <mgorny@gentoo.org>]

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Hello,

Now that python-exec spawns random Python scripts happily, I think we
can consider replacing python-wrapper (the one that spawns Python
itself) with it as well. The idea is similar, and the code is much
simpler here.

However, a bit of hackery would need to be done to change python-exec's
behavior. Right now, it spawns "$0-$EPYTHON" but it will need to just
spawn "$EPYTHON" when run as 'python'. I think we can do it in one
of the following ways:


1) add an 'if' clause to the code, looking for argv[0]~=python.

Simply saying, if python-exec is run as python, just run $EPYTHON,
without prepending $0-. As simple as it can be.

Pros:

- a simple solution.

Cons:

- potentially fragile -- check relies on argv[0]; someone symlinks it
  to a different name -- boom;

- the 'if' check done for every other script where it is irrelevant.


2) add '-$EPYTHON' symlinks to the python interpreters.

So:
  /usr/bin/python-python2.7 -> python2.7
  /usr/bin/python-python2.6 -> python2.6
  /usr/bin/python-pypy-c1.9 -> pypy-c1.9

Pros:

- will work with python-exec as-is.

Cons:

- $PATH pollution.

Note: if we ever wanted to replace Python implementations with
additional wrappers (e.g. trying to fix bug #438984[1]) the 'long
names' could carry the actual Python executables. But that's probably
a bad idea anyway.

[1]:https://bugs.gentoo.org/show_bug.cgi?id=438984


3) add an '#if' clause and build the Python-relevant code conditionally.

In other words, let python-exec install both regular 'python-exec'
and the 'python' binary built from the same code with '#if' switched.

Pros:

- still simple, and clean.

Cons:

- two executables installed.


What are your thoughts?

-- 
Best regards,
Michał Górny

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