Add support for --no-comments to spago init

[jhrcek]

Description of the change

Here's the initial attempt to implement support for --no-comments switch (fix #417)

The most future-proof approach seems to be to parse the dhall template file, remove comments from AST and pretty-print it before writing the file. This however is currently not possible due to dhall stripping most comments while parsing (see dhall-lang/dhall-haskell#145).

This PR could be considered a hack taking advantage of this Dhall behavior and simply does parse + pretty print of dhall templates, which "accidentally" strips comments. This impl. will potentially break in the future when Dhall parser preserves comments, but I added tests to catch this.

I thought of couple of alternative approaches, but I find them even more hacky/brittle than the current PR:

1. Do something like Text.dropWhile (/="-}") on the dhall template files (would break once more than 1 comment is present in the template or comment is somewhere else than in the beginning)
2. Have another "no comment" templates and copy those instead (would require maintenance of duplicate templates)

Checklist:

• Added the change to the "Unreleased" section of the changelog
• Added some example of the new feature to the README
• Added a test for the contribution (if applicable)

P.S.: the above checks are not compulsory to get a change merged, so you may skip them. However, taking care of them will result in less work for the maintainers and will be much appreciated 😊

[f-f]

@jhrcek sorry for taking a while to review. This looks great!
I only left minor comments, but we're almost there 🙂

[jhrcek]

Thanks for the feedback! spago works great and is really useful. Also the source code is nicely readable. I'd like to contribute some more to practice my Haskell :-) Let me know if there are some issues that you'd consider helpful to fix, otherwise I'll pick something with "good first issue" label

[f-f]

@jhrcek thanks for the kind words, I'm happy to hear this 😊

I just went through all the issues marked with "good first issue", and they should all be fine to pick up! I also tried to provide context and/or an idea for implementation in there, but if there are any details missing or confusing I'd be happy to detail more in the relevant threads 🙂

[f-f]

Looks great, thanks for doing this! 👏