mergiraf: use mergiraf cli to generate gitattributes

[drawbu]

Use mergiraf official supported languages list to generate git attributes instead of using a wildcard, as advised in the official documentation.
We generate the git attributes, so we can't rely on testing, or they will break every so often

I'd like your opinion @bobvanderlinden

Description

Checklist

• Change is backwards compatible.

• Code formatted with nix fmt or
  nix-shell -p treefmt nixfmt-rfc-style keep-sorted --run treefmt.

• Code tested through nix-shell --pure tests -A run.all
  or nix build --reference-lock-file flake.lock ./tests#test-all using Flakes.

• Test cases updated/added. See example.

• Commit messages are formatted like

  {component}: {description}
  
  {long description}
  

  See CONTRIBUTING for more information and recent commit messages for examples.

• If this PR adds a new module

  • Added myself as module maintainer. See example.

Maintainer CC

[ambroisie]

This would introduce IFD when enabling the option.

[bobvanderlinden]

I had the same idea initially for the mergiraf module. See the discussion here: #6633 (review)

The main maintainer of mergiraf mentioned using * instead (#6633 (comment)), so I moved to * to avoid IFD.

Do you have an use case where * doesn't suffice?

[drawbu]

Yeah, I don't know how I missed that from the original change you requested on the PR... I did not use a case where * did not suffice, but figured that since it was an explicit requirement in the doc, it was for a good reason. Since it is a change that already has been discussed in the prev PR, I should close it.

Thanks for the message, I guess I'll have to read more carefully next time!