- Spec.copy() does not create superfluous nodes and preserves DAG
connections.
- Spec.normalize() doesn't create extra dependency nodes or throw out
old ones like before.
- Added better test cases for above changes.
Minor things:
- Fixed bug waiting to happen in PackageDB.get()
- instances was keyed by name, not by spec, so caching wasn't really
working at all.
- removed unused PackageDB.compute_dependents function.
- Fixed PackageDB.graph_dependencies() so that spack graph works again.
5f073ae220