Added flake.nix

[YPares]

This adds a flake.nix file so jj-fzf can be installed with its deps with Nix, just like jj.

It uses jj v0.23.0 from nixpkgs.

[tim-janik]

Thanks for the submission.

I am not familiar with nix packaging, so I have a couple questions:

• Where is the dependency on jj-0.23.0 in there, and the fzf version dependency?
• Shouldn't it depend on gnu-sed as well? (MacOS users need that)
• Does it have to add files in the root directory of the project?
• Why is the lock file needed? (With npm, I have had the experience that adding a lock file is usually a bad idea)
• Is there a spec somewhere for flake.nix where I can read up on the details of the format (and possibly answer some of the above questions)?

[YPares]

So all the deps are provided by nixpkgs, which is itself pinned by the flake.lock (that's why it is meant to be committed. nix flakes have no need for version boundaries: everything is pinned by default). The current nixpkgs provide jj-0.23.0 and fzf-0.56.0, that's why you need nothing more. nix flake update --refresh would be the command to update the lockfile (possibly when a new jj or fzf version gets released on nixpkgs). But as long as you don't explicitly update it yourself, downstream users will always be installing a jj-fzf that uses jj 0.23.0 and fzf 0.56.0.

Yeah, the flake.nix should usually be put at the top-level.

Good point about gnu-sed, I'm adding it. Though I'll be unable to test on MacOS

Re. a starting point, I think https://zero-to-nix.com/concepts/flakes is nice.

Since https://github.com/martinvonz/jj is also packaged with a flake.nix, there could also be the option of depending on a dev version of jj (which would be locked & updated in the same way) if you instead want dev versions of jj-fzf to remain more in sync with bleeding-edge jj.

Also, once your project is packaged with a flake, CI/CD comes for free with for instance https://garnix.io/ (with no need for extra config files)

[emilazy]

There is a work‐in‐progress Nixpkgs PR for jj-fzf at NixOS/nixpkgs#353879. It might be good to coordinate, e.g. to use the same package definition so that the flake and Nixpkgs package work the same way.