Summary

Currently some spack config files, particularly packages.yaml for external packages available, but some
aspects of others, are more dependent on the specific operating system (i.e Centos7 vs Centos8) than
the os type (i.e linux) or architecture. It is beneficial then to have a centos7/packages.yaml and a centos8/packages.yaml, etc. listing which packages are local installs on the system, and have Spack
automatically use the right one.

We've been adding this feature locally at Fermilab for several releases now, as it lets us put a single
spack package area in CVMFS that supports multiple OS-es.

Rationale

Without this patch, you need to have a separate spack instance for each OS version, because your packages.yaml file has to be different to use system software packages.

Description

You need simply one more sub-scope routine in config.py -- pull request to follow.

Additional information

This has been an issue with spack 0.16.1, 0.17.1 and 0.18.0

General information

• I have run spack --version and reported the version of Spack
• I have searched the issues of this repo and believe this is not a duplicate