zc.recipe.egg may delete project's source code

[Thomas Lotze]

When switching from the zc.recipe.egg:custom recipe to zc.recipe.egg.script, it may happen that zc.recipe.egg deletes the source code of a develop-egg. To reproduce (for me , this "works" with zc.buildout 1.5):

- Create a minimal develop egg: directories src and src/foo and an empty src/foo/__init__.py plus setup.py and buildout.cfg like this:

setup.py:

from setuptools import setup, find_packages
setup(
    name='foo',
    version='1.0dev',
    packages=find_packages("src"),
    package_dir={"": "src"},
    )

buildout.cfg

[buildout]
parts = foo
develop = .

[foo]
recipe = zc.recipe.egg:custom

- bootstrap and buildout the buildout, everything's still fine

- modify buildout.cfg, switch the recipe to zc.recipe.egg:script

- run bin/buildout, this run doesn't even complete as it has already removed the src directory