fix --no-deps when running autoproj update
fix handling of relative paths in autoproj show

CmdLine.initialize_root_directory was chdir'ing into the root dir,
which was breaking the expansion of relative paths. This commit
expands before calling initialize_root_directory
remove long-unused flag
fix configuration update when --from is given
make the gem manager learn how to share the gem cache

If AUTOBUILD_CACHE_DIR, the downloaded gems will go in $CACHE/gems.
This is done through symlinking, unfortunately, as RubyGems has no
API for it.
Merge branch 'stable'
fix handling of local package sets
add common test setup file
ops/configuration: fix infinite loop in sort_package_sets_by_import_order (closes #30)

The commit ensures that, given a set of packages we must sort, all their
imports are in the queue.
Merge pull request #31 from rock-core/bugfixes

Bugfixes