A given package set can tell autoproj to import another one BEFORE it gets loaded. This is done in the ‘imports’ section of the source.yml file, using the same syntax that in the ‘package_sets’ section of the manifest

For instance, the rock.core package set has

imports:
  - github: orocos-toolchain/autoproj

which means that autoproj will automatically import the orocos toolchain build configuration when the main manifest lists rock.core. It tells you so at checkout with

autoproj: updating remote definitions of package sets
  checking out git:git://github.com/rock-core/package_set branch=master
  rock.core: auto-importing git:git://github.com/orocos-toolchain/autoproj
  checking out git:git://github.com/orocos-toolchain/autoproj

and at update time with

autoproj: updating remote definitions of package sets
  updating rock.core
  rock.core: auto-importing orocos.toolchain
  updating orocos.toolchain

If some imports are not needed (or harmful) to your complete build configuration, they can be disabled package-set-wide either by modifying the manifest or programmatically

Imports will be disabled if you add the “auto_imports: false” flag in the manifest to the package set’s definition:

package_sets:
  - type: git
    url: git://github.com/rock-core/package_set
    auto_imports: false

Or by adding the following statement to autoproj/init.rb:

disable_imports_from 'rock.core'