feat: add tagging for github code navigation

[sielicki]

https://tree-sitter.github.io/tree-sitter/4-code-navigation.html

Code Navigation Systems

Tree-sitter can be used in conjunction with its query language as a part of code navigation systems. An example of such a system can be seen in the tree-sitter tags command, which emits a textual dump of the interesting syntactic nodes in its file argument. A notable application of this is GitHub's support for search-based code navigation. This document exists to describe how to integrate with such systems, and how to extend this functionality to any language with a Tree-sitter grammar.

See also: github docs on code navigation.

tl;dr: I expect that we can get code navigation within nixpkgs such as:

Provided that our grammar supports the tag generation and github is willing to run it. This PR adds two queries that will do that.

Commit:     Nicholas Sielicki <[email protected]>
CommitDate: Mon Mar 31 23:45:39 2025 -0700

feat: add function def/ref tags

quoting tree-sitter docs:
> Tree-sitter can be used in conjunction with its query language as a
> part of code navigation systems. [...] A notable application of this
> is GitHub's support for search-based code navigation.

assuming github is willing to continually run the indexing on a
repository with as much activity as nixpkgs, this should mean that
clicking a function on github allows you to navigate to/from the
definition of the function.

On my laptop, for nixpkgs:
> $ time bash -c "tree-sitter tags --paths <(git ls-files | rg '[.]nix$') >/dev/null 2>&1"
> bash -c   7.40s user 1.14s system 100% cpu 8.501 total

Signed-off-by: Nicholas Sielicki <[email protected]>

2 files changed, 17 insertions(+)
queries/tags.scm | 16 ++++++++++++++++
tree-sitter.json |  1 +

[sielicki]

I wonder if this can be improved further -- right now, package definitions are just all going to resolve to top-level.nix

I'm not sure whether there's enough flexibility in the tagging scheme to properly disambiguate through callPackage/mkDerivation