Instead, prompt the user for missing dataset names. This makes it more predictable and safer which datasets are read and written, and makes it easier to use the tool.

I've been using this tool to compute Christoffel derivs and spatial Ricci tensor in initial data to find horizons:

spectre transform-vol BbhVolume* -k spectre.NumericalAlgorithms.LinearOperators.partial_derivative
# then select 'SpatialChristoffelSecondKind' when prompted

spectre transform-vol BbhVolume* -k spectre.PointwiseFunctions.GeneralRelativity.ricci_tensor
# also select the dataset names when prompted

spectre bbh find-horizon BbhVolume* -l 12 -r 2 -C 8 0 0

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• The code is documented and the documentation renders correctly. Run
  make doc to generate the documentation locally into BUILD_DIR/docs/html.
  Then open index.html.
• The code follows the stylistic and code quality guidelines listed in the
  code review guide.
• The PR lists upgrade instructions and is labeled bugfix or
  new feature if appropriate.

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