python ZipFile module does not support updating an entry in place, instead make
a new zip file and copy all entries.

On Python 3, these made the build output very hard to read (e.g., https://travis-ci.org/buildout/buildout/jobs/394026829)

On Python 3.7, these could actually break the doctests.

Closing the files should get us closer to being able to pass the tests with PyPy.

Because updating a section no longer add the section t the end of parts in
.installed, uninstallation happens in this order.

fixup! Add referred parts' hash strings in __buildout_signature__, that invokes rebuild of a part when one of its (recursive) dependencies are modified.

egg signatures are always {egg_name}-{egg_verson}, there should not be a "egg" prefix for setuptools

fixup! Add referred parts' hash strings in __buildout_signature__, that invokes rebuild of a part when one of its (recursive) dependencies are modified.

Comment by Julien Muchembled:

    Maybe we again have the original behaviour because of
    commit dffdeffc.

    Anyway, the behaviour of buildout at this point is meaningless.
    Buildout was previously invoked with install d3 d4 command-line
    arguments and I consider that d2 should have been reinstalled,
    because a section shall not access the option of another section
    if the latter is not properly installed.

Only build egg at this point if we have some patches to apply otherwise
buildout would install dependent egg without logging this operation, which
would cause many tests to fail.

Also cover the whole scenario of egg patching in a new doctest.

fixup! Add referred parts' hash strings in __buildout_signature__, that invokes rebuild of a part when one of its (recursive) dependencies are modified.

Add a RENormalizer so the easy_install.txt will be happy with scripts
generated on Python 2 (using open(..., 'U')) and on Python 3 (using just
open(...)).

This was suggested by @sallner.

(cherry picked from commit 2cf42066fc8238ffe72ce6aeaef0e66b5df13f79)

Python 3.7 began warning about open's 'U' mode. Universal newline mode (newline=None) is default in Python 3 so avoid specifying it on Python 3.

(cherry picked from commit 978a6af9e78db44b9db25cb08c7f9d98c24bbc03)

If a.cfg extends b.cfg and both contain [a],
it was already not possible for a.cfg:[a] to combine <= & +=.
But it worked when a.cfg:[a] does not extend anything, and
commit 161fb191 broke that.

The only proper way to solve all this seems to process <= before
+= & -=. But since processing <= while extending files would cause
other issues, we'd rather process +=&-= when initializing parts.

extends can be interpreted as inheritance in OOP, but the original
behaviour was against what is commonly (always?) seen everywhere.

It is however good practice a file extends all files it needs directly
(and only them). Then if two files A & B (possibly unrelated) extends
the same third C, A was unable to overrides C values. It was even
error-prone because someone who don't use B yet could override C values
in A and later extending B would break A.

For some of our common use cases, this new algorithm is also 9x faster
(time to annotate: ~2.3s with -> ~.29s).

Other changes:
- ~/ is now expanded for non-url extends.
- An absolute (non-url) path is not longer treated like a local path
  if the base is a url.
- Better path/url normalization.

Rebase instructions:
- squash with "Chomp ../ from beginging of filenames"
- split and apply "Support ${:_profile_base_location_}." after

Revert "Cache downloaded data in zc/buildout/buildout.py:_open() in memory to accelerate remote extends."

This reverts commit 260bc0c4 partially.

The remaining should be squashed with "Write .installed.cfg only once, in safe way and only if there's any change."

We want two identical sections at different URL to be able to produce
same signature. This is feature is useful for slapos.recipe.cmmi's
shared parts.

Rebase instructions:
- squash with "apply "Support ${:_profile_base_location_}."

If we use options.items() we visit all keys and not used options cannot
be detected.

Rebase instructions:
- squash with "Add referred parts' hash strings in
  __buildout_signature__, that invokes rebuild of a part
  when one of its (recursive) dependencies are modified"
- add a comment explaining why such a lower level API is used

This is useful when using OS Python & eggs.

Useless for SlapOS.

fixup! Add referred parts' hash strings in __buildout_signature__, that invokes rebuild of a part when one of its (recursive) dependencies are modified.

The purpose is to make the part signature available sooner,
during recipe's __init__.

Commit 8be81fe4 already
broke detection of unused options in sections.

The version of Python should not affect the behaviour of a recipe.
Anyway, it was already ignored for DEVELOP_DIST eggs.

This makes the slapos mechanism to share parts more efficient. And with
the upcoming changes in buildout & slapos.recipe.cmmi, there would be
no way for the slapos.reboostrap extension to prevent everything from
being rebuilt when reboostrapping to a different version of Python,
if bootstrap parts are shared.

The monkey-patch by slapos.reboostrap now becomes useless.

When buildout encounter an error, program exists with error code 1, this
should also be the case when exiting from a debugger session when
running with -D option.

/reviewed-on !17

When a recipe is developed in a git working copy, .git administrative
database folder should be ignored, like we did with CVS and svn.

/reviewed-on !14

_install_and_load is slow, using cache saves time when there are many sections.

Contrary to bash, dash filters out environment variables
containing '-' characters.