This led to a pretty major refactoring.

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It wasn't possible to give options on the command line for sections
not defined in a configuration file.

  to avoid database corruption when a user breaks out of a buildout
  with control-c.

- Don't save an installed database if there are no installed parts or
  develop egg links.

sections.

Treat DistutilsErrors as user errors.

- Added "logical tracebacks" that show functionally what the buildout
  was doing when an error occurs.  Don't show a Python traceback
  unless the -D option is used.

- Added a -D option that causes the buildout to print a traceback and
  start the pdb post-mortem debugger when an error occurs.

be specified in a versions section.

Changed the log format for picked versions.

This will allow a versions feature to be added without updating all
recipes initially.  Later, recipes that support custom versions will
be able to override the defaults by passing options.

- The easy_install module install and build functions now accept a
  versions argument that supplied to mapping from project name to
  version numbers.  This can be used to fix version numbers for
  required distributions and their depenencies.

When a version isn't fixed, using either a versions option or using
  a fixed version number in a requirement, then a debug log message is
  emitted indicating the version picked.  This is useful for setting
  versions options.

- Added a remove testing helper function that removes files or directories.

no longer causes voluminous setuptools output.  Uisng -vv and -vvv
now triggers extra setuptools output.

Improved a logging message.

spurious test failures.  I'm not sure this is really necessary.

```------------
- Added a buildout newest option, to control whether the newest
  distributions should be sought to meet requirements.  This might
  also provide a hint to recipes that don't deal with
  distributions. For example, a recipe that manages subversion
  checkouts might not update a checkout if newest is set to "false".

- The recipe-testing support setUp function now adds the name
  *buildout* to the test namespace with a value that is the path to
  the buildout script in the sample buildout.  This allows tests to
  use

>>> print system(buildout),

rather than:

>>> print system(join('bin', 'buildout')),

Bugs Fixed
```

-------

- Paths returned from update methods replaced lists of installed files
  rather than augmenting them.

Also added a missing tests for upgrading.