By default, do not constrain doctest

[andreasabel]

doctest bound has been rotting too quickly.
Just use the latest version by default.
Can always be overwritting by doctest-version option in cabal.haskell-ci.

Closes #690

[phadej]

You can specify doctest-version: >=0 in your configuration file.

[andreasabel]

You can specify doctest-version: >=0 in your configuration file.

Yes of course.
But good tooling has sensible defaults. Defaulting to an outdated version isn't a good default.

Removing the constraint would lead to the following workflow:

1. Usually doctest: True does the job.
2. A user that needs an older version of doctest would go looking for a way to configure the doctest version used by haskell-ci.

Currently we have:

1. The doctests fail.
2. The user may discover that nothing is wrong other than haskell-ci pinning to an outdated version.
3. The user wonders where this pin comes from as they haven't specified the doctest version.

[phadej]

Currently we have:

The doctests fail.

Do we? If they worked, they should continue to work.

And that "if it worked, and nothing is explicitly changed, it should work" is my philosophy. You may upgrade haskell-ci (which may have different major version used by default), or change the haskell-ci config or do something else - then things may break (or unbreak) - but you'll know what you have changed.

You won't make me change my mind on this.

[andreasabel]

Do we? If they worked, they should continue to work.

If they weren't broken, I wouldn't have gone to the effort of changing Haskell CI.
Let me see if I can recover the evidence...

Got it!

• here is the commit that dropped the doctest bound: andreasabel/generic-lens@e8428f7
• here is the CI run that documents that the old doctest fails to install on GHC 9.8: https://github.com/andreasabel/generic-lens/actions/runs/6970245848/job/18967757841
• here is the CI run that documents the the new doctest succeeds to install on GHC 9.8: https://github.com/andreasabel/generic-lens/actions/runs/6970602089/job/18968859617#step:11:27

[phadej]

If they weren't broken,

You added GHC-9.8 CI, so you did change something.