Feature: Allow ignore file pattern in environment views

[wdconinc]

The environment spack.yaml section on views should be able to have a file pattern that should be ignored, e.g.

spack:
  views:
    all:
      ignore: [.cvmfscatalog]

This would avoid FileExistsError exceptions when creating views due to the presence of these files.

Rationale

Since all cvmfs catalog have the same name, they are creating conflicts.

Description

Currently, an additional step in environment creating and publishing is first removing all cvmfscatalog files, then creating the environment, then recreating all cvmfscatalog files. This could happen while a cvmfs release is in progress, resulting in missing cvmfs catalog files and reduced performance.

Additional information

Relevant line in the code: https://github.com/spack/spack/blob/develop/lib/spack/spack/filesystem_view.py#L374

General information

• I have run spack --version and reported the version of Spack 0.15.4-51-9ff859acd
• I have searched the issues of this repo and believe this is not a duplicate

This has been discussed with becker33 in the spack slack channel.