Share code in fields of queries

[smelc]

Changelog

- description: |
    Share code in fields of queries
# uncomment types applicable to the change:
  type:
  # - feature        # introduces a new feature
  # - breaking       # the API has changed in a breaking way
  # - compatible     # the API has changed but is non-breaking
  # - optimisation   # measurable performance improvements
  - refactoring    # QoL changes
  # - bugfix         # fixes a defect
  # - test           # fixes/modifies tests
  # - maintenance    # not directly related to the code
  # - release        # related to a new release preparation
  # - documentation  # change in code docs, haddocks...

Context

Fixes #983

How to trust this PR

• This is one of the PRs where, if it typechecks, it works.
• -292+225

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• Self-reviewed the diff

[Jimbo4350]

We should exclude the output file from the refactor. It's a UI wart IMO but the rest of the refactor is 👍. I'm sure @CarlosLopezDeLara would agree here. I also think leaving the original out-file help is more informative.

[Jimbo4350]

Why the change? It was more informative before.

[Jimbo4350]

This is the downside of the refactor. It affects the parsers and I would argue having --out-file as the last argument is more natural. More and more I wish for monadic parsers.