Fix mapping MPAS-O to Omega config options

[xylar]

The mapping now works given MPAS-O config options that map to Omega config options with non-unique names and nested section names.

Checklist

• Testing comment in the PR documents testing used to verify the changes

Fixes #450

[xylar]

Testing

This worked for me in combination with #435 (after commenting out a few model config options that aren't supported on the Omega develop branch). In particular, in ocean/single_column/vmix_stable/forward_constant/omega.yml, I see:

  VertMix:
    Background:
      Diffusivity: 1.0e-5
      Viscosity: 1.0e-4
    Convective:
      Enable: false
      Diffusivity: 1.0
      TriggerBVF: 0.0
    Shear:
      Enable: false
      NuZero: 0.005
      Alpha: 5.0
      Exponent: 2.0

Both convective and shear mixing are disabled, as desired.

[xylar]

@cbegeman, could you cherry-pick this commit and confirm that it fixes #450 for you as well?

[cbegeman]

@xylar Am I understanding correctly that in the MPAS-O to Omega mapping, we don't actually use MPAS-O section names, keeping it None, simply because we don't need to since MPAS-O config option names are unique?

[xylar]

@xylar Am I understanding correctly that in the MPAS-O to Omega mapping, we don't actually use MPAS-O section names, keeping it None, simply because we don't need to since MPAS-O config option names are unique?

Yes, exactly. And not editing all the locations where we currently set config options without providing an MPAS-O section will save a lot of tedium. We will eventually have to address this when we switch to Omega --> MPAS-O mapping instead of the reverse, but we can punt on that for now.

[cbegeman]

This fix resolves the issue for me as well. Thanks for your help with this!

[xylar]

Great! Thanks for the review, @cbegeman!