Topiary integration as nickel format

[vkleen]

Add a nickel format subcommand to the CLI, gated behind the format feature flag. The nix flake outputs nickel and nickel-static enable format by default.

The nickel format subcommand is a thin wrapper around Topiary and embeds the required tree-sitter queries for Nickel formatting.

Status:

• Formatting with Topiary
• Don't vendor the tree-sitter query file, depends on upstream Topiary support
• Static executables

[vkleen]

I'm marking this as ready for review, even though static linking isn't quit figured out yet. The formatting subcommand is gated behind a feature flag and currently disabled for the static build. We can enable the feature flag for the static build once we figure out how to get it to work.

[yannham]

The structure of the CLI looks better like this 👍 I'm requesting changes to not forget to disable the format feature for now, until we figure out the static build story.

[yannham]

Don't we want to disable it by default for this PR, until we figure out the static binary build story?

[vkleen]

We can keep it enabled for the normal CLI build, and just disable it for the static binary. That way at least nix run github:tweag/nickel gets the formatting feature.

[yannham]

Ah, what I understood as "principle of least surprise" from the last planning meeting was that the binary built/run from nix with the default command and the one provided as a static binary shouldn't differ, as you should expect as a user. I would vote for disabling everywhere for now, but just merge it, so that this PR doesn't drift away from the master branch.

[aspiwack]

It's what I meant. But I don't think you need to choose how you're going to handle it before you release.

[vkleen]

Alright, I've disabled the format feature for the nix build 👍