git: Add option to use difftastic as diff tool

[notarock]

Description

Add the option to use difftastic, a syntax-aware diff tool, with git

Checklist

• Change is backwards compatible.

• Code formatted with ./format.

• Code tested through nix-shell --pure tests -A run.all.

• 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.

  • Added myself and the module files to .github/CODEOWNERS.

[notarock]

Pretty sure it would be good to only allow to enable one of either difftastic or delta but I am not too familiar with nix, how can I achieve this?

[sumnerevans]

sorry, one more thing

[sumnerevans]

Also, please squash your commits to a single one that follows the contributing guide for commit messages.

[notarock]

Thanks for the review, I fixed it. Sorry for the constant back-and-forth, hopefully this is good now 😅

[sumnerevans]

Thanks! difftastic seems nice

[lobre]

Hello @notarock,

Is there for convenience that you set the pager in that MR? I don’t see it mentioned in the documentation.

home-manager/modules/programs/git.nix

Line 483 in 5872aad

core.pager = "${pkgs.less}/bin/less -XF";

https://difftastic.wilfred.me.uk/git.html

I like to set my own core.pager to less -+FX to enable mouse scroll. But when I am enabling difftastic, it conflicts and I cannot define my own config anymore.

Is it possible to keep that option free for the end user?

[sumnerevans]

Maybe we need to do core.pager = mkDefault ...?

[notarock]

Is there for convenience that you set the pager in that MR?

No particular reasons really, it just made the output play nice enough for me when I first contributed the module.

[lobre]

No particular reasons really, it just made the output play nice enough for me when I first contributed the module.

@notarock, would you agree to having it removed, or maybe using mkDefault to avoid forcing it on users?

[notarock]

would you agree to having it removed, or maybe using mkDefault to avoid forcing it on users?

I don't have an opinion on this. Making it configurable with a default value seems like the way to go, but I don't have time to submit a pull request at this time. Feel free to open one if needed

[lobre]

I decided to stick with the default git diff algorithm at the end instead of using difftastic. Making it configurable is the solution, but I will also let that duty of creating a PR to anyone requiring it in the future.

Thanks anyway for helping with that.