Extends option does not expand variables

[claytron]

URLs in the extends option are not expanded to use buildout variables. Here is an example that does not work.

[buildout]
plone-version = 4.0.1
extends = http://dist.plone.org/release/${:plone-version}/versions.cfg

This will result in an error saying that the literal address does not exist.

[Benoît Bryon (benoit.bryon)]

I am experiencing the same issue.

Version of buildout: 1.5.2.

My use case is to extend configuration files from various locations within the buildout directory.
As an example, with 3 files:

* buildout.cfg, which extends etc/buildout/project.cfg. Works fine.
* etc/buildout/project.cfg, which extends src/project/base.cfg.

  * fails if I use "extends = ${buildout:directory}/etc/buildout/versions.cfg".
  * works if I use "extends = ../../etc/buildout/versions.cfg", but I'd prefer rely on ${buildout:directory} than use relative paths.

* and src/project.base.cfg, no matter what it does.